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-codebase-graph/src/navigation.rs

@@ -238,7 +238,7 @@ impl Navigator {
     ///
     /// # Arguments
     /// * `file_path` - Path to the file
-    /// * `row` - 1-indexed line number  
+    /// * `row` - 1-indexed line number
     /// * `col` - 1-indexed column number
     /// * `include_definition` - Whether to include the definition location in results
     ///
@@ -388,8 +388,8 @@ fn is_identifier_like(node: &tree_sitter::Node<'_>) -> bool {
             | "field_identifier"
             | "shorthand_property_identifier"
             | "shorthand_property_identifier_pattern"
-            | "attribute"           // Python
-            | "package_identifier" // Go
+            | "attribute"
+            | "package_identifier"
     )
 }