style(context): bersihkan warning clippy pedantic di squash.rs dan dedup.rs

Perbaikan gaya murni (format! di-append ke String -> write!, syntax
perbandingan yang lebih jelas, backtick di doc comment) tanpa
mengubah perilaku -- semua test tetap hijau.

src/app/runtime/context/squash.rs

@@ -12,6 +12,7 @@
 //! overall budget.
 
 use std::collections::HashSet;
+use std::fmt::Write;
 
 /// Below this size, compression isn't worth the risk of losing detail —
 /// pass the output through unchanged.
@@ -249,7 +250,7 @@ fn squash_generic(text: &str, budget: usize) -> String {
     let mut prev = "";
     for (i, &line) in lines.iter().enumerate().take(tail_start).skip(head_end) {
         let non_trivial = !line.trim().is_empty() && line != prev;
-        if non_trivial && used + line.len() + 1 <= budget {
+        if non_trivial && used + line.len() < budget {
             keep.insert(i);
             used += line.len() + 1;
         }
@@ -269,14 +270,14 @@ fn render_kept_lines(lines: &[&str], keep: &HashSet<usize>) -> String {
     let mut cursor = 0usize;
     for &i in &kept_sorted {
         if i > cursor {
-            out.push_str(&format!("[{} lines omitted]\n", i - cursor));
+            let _ = writeln!(out, "[{} lines omitted]", i - cursor);
         }
         out.push_str(lines[i]);
         out.push('\n');
         cursor = i + 1;
     }
     if cursor < lines.len() {
-        out.push_str(&format!("[{} lines omitted]\n", lines.len() - cursor));
+        let _ = writeln!(out, "[{} lines omitted]", lines.len() - cursor);
     }
     out
 }