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-subagent-resolution/src/resume.rs

@@ -92,7 +92,7 @@ mod tests {
         }
     }
 
-    // ── Matching cases ───────────────────────────────────────────
+    // Matching cases
 
     #[test]
     fn matching_type_no_persona() {
@@ -131,7 +131,7 @@ mod tests {
         assert!(result.is_ok());
     }
 
-    // ── Mismatching cases ────────────────────────────────────────
+    // Mismatching cases
 
     #[test]
     fn type_mismatch_rejected() {
@@ -168,7 +168,7 @@ mod tests {
         ));
     }
 
-    // ── Validation order ─────────────────────────────────────────
+    // Validation order
 
     #[test]
     fn type_mismatch_checked_before_persona() {