feat(view): Tambah parameter dim dan pewarnaan baris diff di markdown renderer

Tambahkan helper apply_dim dan diff_line_style, ubah signature
render_markdown untuk menerima flag dim, serta deteksi fence bahasa
diff sehingga baris +/-/@@ tetap berwarna meskipun pesan sedang
dirender dim (tampilan tool-output).

src/view/markdown.rs

@@ -19,21 +19,54 @@ use ratatui::style::{Modifier, Style};
 use ratatui::text::Span;
 use super::theme::Theme;
 
+/// Apply the "tool output" dim/italic style, or pass `style` through
+/// unchanged, depending on `dim`.
+fn apply_dim(style: Style, dim: bool) -> Style {
+    if dim {
+        Style::default().fg(Theme::TEXT_DIM).add_modifier(Modifier::ITALIC)
+    } else {
+        style
+    }
+}
+
+/// Classify a single line inside a ` ```diff ` fenced block by its unified-diff
+/// prefix, returning the color it should always render with (even when the
+/// surrounding tool output is dimmed) — or `None` for context lines and the
+/// `+++`/`---` file-header lines, which use the normal code-block color.
+fn diff_line_style(line: &str) -> Option<Style> {
+    if line.starts_with("@@") {
+        Some(Style::default().fg(Theme::INFO).bg(Theme::CODE_BG))
+    } else if line.starts_with('+') && !line.starts_with("+++") {
+        Some(Style::default().fg(Theme::SUCCESS).bg(Theme::CODE_BG))
+    } else if line.starts_with('-') && !line.starts_with("---") {
+        Some(Style::default().fg(Theme::ERROR).bg(Theme::CODE_BG))
+    } else {
+        None
+    }
+}
+
 /// Render a markdown string into styled terminal spans, word-wrapped to `width`.
 ///
 /// Flow: `pulldown_cmark` parses `text` into an event stream → each
 /// Start/End/Text/Code/Break event is translated into styled `Span`s →
 /// if `width > 0`, a second pass wraps long lines.
 ///
+/// `dim`: when `true`, every span falls back to `Theme::TEXT_DIM` + italic
+/// (the "tool output" look) *except* lines inside a ` ```diff ` fenced
+/// block, which always keep their +/-/@@ diff color regardless of `dim` —
+/// this is what lets diff output stay colored inside otherwise-dimmed
+/// `Role::Tool` chat messages.
+///
 /// Return: a flat vec of styled spans; `chat::split_spans_into_lines`
 /// turns it back into `Line`s for the Paragraph widget.
 #[allow(clippy::too_many_lines)]
-pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
+pub fn render_markdown(text: &str, width: u16, dim: bool) -> Vec<Span<'static>> {
     let mut spans = Vec::new();
     let mut options = pulldown_cmark::Options::empty();
     options.insert(pulldown_cmark::Options::ENABLE_TABLES);
     let parser = pulldown_cmark::Parser::new_ext(text, options);
     let mut in_code_block = false;
+    let mut in_diff_block = false;
     let mut in_heading = false;
     let mut heading_level = 0;
     
@@ -46,8 +79,12 @@ pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
         match event {
             pulldown_cmark::Event::Start(tag) => {
                 match tag {
-                    pulldown_cmark::Tag::CodeBlock(_) => {
+                    pulldown_cmark::Tag::CodeBlock(kind) => {
                         in_code_block = true;
+                        in_diff_block = matches!(
+                            &kind,
+                            pulldown_cmark::CodeBlockKind::Fenced(lang) if lang.as_ref() == "diff"
+                        );
                         // Code block top bar
                         spans.push(Span::styled(
                             "\n",
@@ -55,7 +92,7 @@ pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
                         ));
                         spans.push(Span::styled(
                             "  ┌─ code ",
-                            Style::default().fg(Theme::TEXT_MUTED).bg(Theme::CODE_BG),
+                            apply_dim(Style::default().fg(Theme::TEXT_MUTED).bg(Theme::CODE_BG), dim),
                         ));
                         spans.push(Span::styled(
                             "\n",
@@ -76,25 +113,25 @@ pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
                         // List item bullet
                         spans.push(Span::styled(
                             "• ",
-                            Style::default().fg(Theme::PRIMARY),
+                            apply_dim(Style::default().fg(Theme::PRIMARY), dim),
                         ));
                     }
                     pulldown_cmark::Tag::Link { dest_url, .. } => {
                         spans.push(Span::styled(
                             "[",
-                            Style::default().fg(Theme::INFO),
+                            apply_dim(Style::default().fg(Theme::INFO), dim),
                         ));
                         // We push the URL as a tooltip-like suffix
                         // After the link text ends, we'll add the URL
                         spans.push(Span::styled(
                             format!("]({dest_url})"),
-                            Style::default().fg(Theme::TEXT_MUTED).add_modifier(Modifier::ITALIC),
+                            apply_dim(Style::default().fg(Theme::TEXT_MUTED).add_modifier(Modifier::ITALIC), dim),
                         ));
                     }
                     pulldown_cmark::Tag::BlockQuote(_) => {
                         spans.push(Span::styled(
                             "▎",
-                            Style::default().fg(Theme::BLOCKQUOTE_BAR),
+                            apply_dim(Style::default().fg(Theme::BLOCKQUOTE_BAR), dim),
                         ));
                     }
                     pulldown_cmark::Tag::Table(_) => {
@@ -114,10 +151,11 @@ pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
                 match tag {
                     pulldown_cmark::TagEnd::CodeBlock => {
                         in_code_block = false;
+                        in_diff_block = false;
                         // Code block bottom bar
                         spans.push(Span::styled(
                             "\n  └─\n",
-                            Style::default().fg(Theme::TEXT_MUTED).bg(Theme::CODE_BG),
+                            apply_dim(Style::default().fg(Theme::TEXT_MUTED).bg(Theme::CODE_BG), dim),
                         ));
                     }
                     pulldown_cmark::TagEnd::Heading(_) => {
@@ -182,7 +220,7 @@ pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
                             let max_height = cell_lines.iter().map(|cl| cl.len()).max().unwrap_or(1);
 
                             for y in 0..max_height {
-                                spans.push(Span::styled("  | ", Style::default().fg(Theme::BORDER)));
+                                spans.push(Span::styled("  | ", apply_dim(Style::default().fg(Theme::BORDER), dim)));
                                 for (i, cl) in cell_lines.iter().enumerate() {
                                     let line_spans = if y < cl.len() { &cl[y] } else { [].as_slice() };
                                     let mut line_width = 0;
@@ -192,15 +230,15 @@ pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
                                     }
                                     let pad = col_widths[i].saturating_sub(line_width);
                                     spans.push(Span::raw(" ".repeat(pad)));
-                                    spans.push(Span::styled(" | ", Style::default().fg(Theme::BORDER)));
+                                    spans.push(Span::styled(" | ", apply_dim(Style::default().fg(Theme::BORDER), dim)));
                                 }
                                 spans.push(Span::raw("\n"));
                             }
 
                             if r == 0 {
-                                spans.push(Span::styled("  |", Style::default().fg(Theme::BORDER)));
+                                spans.push(Span::styled("  |", apply_dim(Style::default().fg(Theme::BORDER), dim)));
                                 for w in &col_widths {
-                                    spans.push(Span::styled(format!("{}-|", "-".repeat(*w + 2)), Style::default().fg(Theme::BORDER)));
+                                    spans.push(Span::styled(format!("{}-|", "-".repeat(*w + 2)), apply_dim(Style::default().fg(Theme::BORDER), dim)));
                                 }
                                 spans.push(Span::raw("\n"));
                             }
@@ -213,11 +251,25 @@ pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
             pulldown_cmark::Event::Text(text) => {
                 let s = text.to_string();
                 if in_code_block {
+                    if in_diff_block {
+                        for (i, line) in s.split('\n').enumerate() {
+                            if i > 0 {
+                                spans.push(Span::raw("\n"));
+                            }
+                            if line.is_empty() {
+                                continue;
+                            }
+                            let style = diff_line_style(line)
+                                .unwrap_or_else(|| Style::default().fg(Theme::ACCENT_TEAL).bg(Theme::CODE_BG));
+                            spans.push(Span::styled(format!("  {line}"), style));
+                        }
+                    } else {
                         let indented = format!("  {}", s.replace('\n', "\n  "));
                         spans.push(Span::styled(
                             indented,
-                        Style::default().fg(Theme::ACCENT_TEAL).bg(Theme::CODE_BG),
+                            apply_dim(Style::default().fg(Theme::ACCENT_TEAL).bg(Theme::CODE_BG), dim),
                         ));
+                    }
                 } else if in_heading {
                     let color = match heading_level {
                         1 => Theme::PRIMARY,
@@ -227,21 +279,24 @@ pub fn render_markdown(text: &str, width: u16) -> Vec<Span<'static>> {
                     };
                     spans.push(Span::styled(
                         s,
-                        Style::default().fg(color).add_modifier(Modifier::BOLD),
+                        apply_dim(Style::default().fg(color).add_modifier(Modifier::BOLD), dim),
                     ));
                 } else if in_table_cell {
-                    current_cell.push(Span::raw(s));
+                    current_cell.push(Span::styled(s, apply_dim(Style::default(), dim)));
                 } else {
-                    spans.push(Span::raw(s));
+                    spans.push(Span::styled(s, apply_dim(Style::default(), dim)));
                 }
             }
             pulldown_cmark::Event::Code(text) => {
                 let span = Span::styled(
                     format!(" {text} "),
+                    apply_dim(
                         Style::default()
                             .fg(Theme::ACCENT_TEAL)
                             .bg(Theme::CODE_BAR)
                             .add_modifier(Modifier::BOLD),
+                        dim,
+                    ),
                 );
                 if in_table_cell {
                     current_cell.push(span);
@@ -377,3 +432,46 @@ fn wrap_spans_to_lines(spans: &[Span<'static>], target_width: usize) -> Vec<Vec<
     }
     lines
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn span_text(spans: &[Span<'static>]) -> String {
+        spans.iter().map(|s| s.content.as_ref()).collect()
+    }
+
+    #[test]
+    fn dim_false_plain_text_has_no_color() {
+        let spans = render_markdown("hello world", 0, false);
+        assert_eq!(span_text(&spans), "hello world");
+        assert_eq!(spans[0].style, Style::default());
+    }
+
+    #[test]
+    fn dim_true_plain_text_is_dim_italic() {
+        let spans = render_markdown("hello", 0, true);
+        let expected = Style::default().fg(Theme::TEXT_DIM).add_modifier(Modifier::ITALIC);
+        assert_eq!(spans[0].style, expected);
+    }
+
+    #[test]
+    fn dim_true_diff_lines_keep_their_own_color() {
+        let md = "```diff\n@@ -1,2 +1,2 @@\n-old line\n+new line\n context line\n```";
+        let spans = render_markdown(md, 0, true);
+        let plus_span = spans.iter().find(|s| s.content.contains("+new line")).expect("plus span present");
+        assert_eq!(plus_span.style.fg, Some(Theme::SUCCESS));
+        let minus_span = spans.iter().find(|s| s.content.contains("-old line")).expect("minus span present");
+        assert_eq!(minus_span.style.fg, Some(Theme::ERROR));
+        let hunk_span = spans.iter().find(|s| s.content.contains("@@")).expect("hunk header span present");
+        assert_eq!(hunk_span.style.fg, Some(Theme::INFO));
+    }
+
+    #[test]
+    fn dim_true_non_diff_code_block_is_dimmed() {
+        let md = "```rust\nfn main() {}\n```";
+        let spans = render_markdown(md, 0, true);
+        let code_span = spans.iter().find(|s| s.content.contains("fn main")).expect("code span present");
+        assert_eq!(code_span.style, Style::default().fg(Theme::TEXT_DIM).add_modifier(Modifier::ITALIC));
+    }
+}