Implement chat and markdown views, enhance status bar, and add workflow panel

- Added `chat.rs` for rendering chat messages with timestamps and roles.
- Introduced `markdown.rs` for rendering markdown content with styling.
- Created `status.rs` to display the application status bar with session and message counts.
- Developed `workflow.rs` to show the current workflow status, including tool calls and active jobs.
- Established a `theme.rs` for centralized color management across the UI.
- Updated `mod.rs` to include new modules and manage rendering logic.

src/model/session.rs

@@ -0,0 +1,85 @@
+use std::path::{Path, PathBuf};
+use serde::{Deserialize, Serialize};
+use chrono::Utc;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Session {
+    pub id: String,
+    pub created_at: i64,
+    pub updated_at: i64,
+    pub title: String,
+    pub model: String,
+    pub workspace_roots: Vec<PathBuf>,
+    pub message_count: u32,
+    pub token_count: u32,
+    pub archived: bool,
+    pub summary: Option<String>,
+}
+
+impl Session {
+    pub fn new(id: String, title: String) -> Self {
+        let now = Utc::now().timestamp_millis();
+        Session {
+            id,
+            created_at: now,
+            updated_at: now,
+            title,
+            model: "anthropic/claude-opus-4-8".to_string(),
+            workspace_roots: vec![std::env::current_dir().unwrap_or_default()],
+            message_count: 0,
+            token_count: 0,
+            archived: false,
+            summary: None,
+        }
+    }
+
+    pub fn session_dir(&self, base_dir: &Path) -> PathBuf {
+        base_dir.join("sessions").join(&self.id)
+    }
+
+    pub fn conversation_path(&self, base_dir: &Path) -> PathBuf {
+        self.session_dir(base_dir).join("conversation.json")
+    }
+
+    pub fn edit_log_path(&self, base_dir: &Path) -> PathBuf {
+        self.session_dir(base_dir).join("edits.jsonl")
+    }
+
+    pub fn msglog_path(&self, base_dir: &Path) -> PathBuf {
+        self.session_dir(base_dir).join("msglog.db")
+    }
+
+    pub fn save(&self, base_dir: &Path) -> std::io::Result<()> {
+        let dir = self.session_dir(base_dir);
+        std::fs::create_dir_all(&dir)?;
+        let path = dir.join("session.json");
+        let data = serde_json::to_string_pretty(self)?;
+        let tmp = dir.join("session.json.tmp");
+        std::fs::write(&tmp, data)?;
+        std::fs::rename(&tmp, path)?;
+        Ok(())
+    }
+
+    pub fn load(id: &str, base_dir: &Path) -> std::io::Result<Self> {
+        let path = base_dir.join("sessions").join(id).join("session.json");
+        let data = std::fs::read_to_string(path)?;
+        let session: Session = serde_json::from_str(&data)?;
+        Ok(session)
+    }
+
+    pub fn list(base_dir: &Path) -> Vec<Self> {
+        let sessions_dir = base_dir.join("sessions");
+        let entries = match std::fs::read_dir(&sessions_dir) {
+            Ok(e) => e,
+            Err(_) => return Vec::new(),
+        };
+        entries
+            .filter_map(|e| e.ok())
+            .filter(|e| e.path().is_dir())
+            .filter_map(|e| {
+                let id = e.file_name().to_string_lossy().to_string();
+                Session::load(&id, base_dir).ok()
+            })
+            .collect()
+    }
+}