docs(comments): rewrite comments across all crates to the guidelines

Sweep every first-party crate source (1956 .rs files) to the project comment
guidelines: delete redundant restatements, decorative banners, change
narration, and end-of-line comments; keep and tighten the crucial ones
(invariants, bug rationale, SAFETY blocks, ported-source attribution).

No functional code changed. Every edit is proven comment-only against the
prior tree by a comment-stripping lexer (string/char/raw-string aware) plus a
separate doctest-fence check. Where removing a comment made rustfmt or clippy
want to re-lay-out adjacent code, the minimal triggering comment is restored so
code tokens stay byte-identical.

Gates green: cargo fmt --all --check (0 diffs), cargo check and cargo clippy
--workspace --all-targets (0 warnings).

Adds scripts/check_codegen_comment_guidelines.py — the enforcement gate for
these guidelines (flags banners, end-of-line comments, change narration, and
commented-out code).

crates/codegen/kigi-workspace/src/file_system/fuzzy.rs

@@ -265,7 +265,8 @@ impl FuzzyFileMatcher {
                 .filter(|e| !self.dirs || e.is_dir)
                 .take(k)
                 .cloned()
-                .collect(); // should be already sorted
+                // should be already sorted
+                .collect();
         }
 
         // https://github.com/helix-editor/helix/blob/d79cce4e4bfc24dd204f1b294c899ed73f7e9453/helix-term/src/ui/completion.rs#L369
@@ -280,8 +281,7 @@ impl FuzzyFileMatcher {
 
         while items.len() < k
             && let Some(m) = iter.next()
-            // for empty queries, return everything; otherwise, apply heuristic min-score limit
-            && (self.query.is_empty() ||  m.score >= min_score)
+            && (self.query.is_empty() || m.score >= min_score)
         {
             fn extract_match(
                 m: &Match,