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-ratatui-textarea/src/render/line_utils.rs

@@ -1,7 +1,6 @@
 use ratatui::text::Line;
 use ratatui::text::Span;
 
-/// Clone a borrowed ratatui `Line` into an owned `'static` line.
 pub fn line_to_static(line: &Line<'_>) -> Line<'static> {
     Line {
         style: line.style,
@@ -17,15 +16,14 @@ pub fn line_to_static(line: &Line<'_>) -> Line<'static> {
     }
 }
 
-/// Append owned copies of borrowed lines to `out`.
 pub fn push_owned_lines<'a>(src: &[Line<'a>], out: &mut Vec<Line<'static>>) {
     for l in src {
         out.push(line_to_static(l));
     }
 }
 
-/// Consider a line blank if it has no spans or only spans whose contents are
-/// empty or consist solely of spaces (no tabs/newlines).
+/// Blank means no spans, or only spans whose contents are empty or consist
+/// solely of spaces; a tab or newline makes the line non-blank.
 pub fn is_blank_line_spaces_only(line: &Line<'_>) -> bool {
     if line.spans.is_empty() {
         return true;
@@ -35,8 +33,6 @@ pub fn is_blank_line_spaces_only(line: &Line<'_>) -> bool {
         .all(|s| s.content.is_empty() || s.content.chars().all(|c| c == ' '))
 }
 
-/// Prefix each line with `initial_prefix` for the first line and
-/// `subsequent_prefix` for following lines. Returns a new Vec of owned lines.
 pub fn prefix_lines(
     lines: Vec<Line<'static>>,
     initial_prefix: Span<'static>,

crates/codegen/kigi-ratatui-textarea/src/wrapping.rs

@@ -553,7 +553,8 @@ mod tests {
 
     #[test]
     fn line_height_counts_double_width_emoji() {
-        let line = "😀😀😀".into(); // each emoji ~ width 2
+        // each emoji ~ width 2
+        let line = "😀😀😀".into();
         assert_eq!(word_wrap_line(&line, 4).len(), 2);
         assert_eq!(word_wrap_line(&line, 2).len(), 3);
         assert_eq!(word_wrap_line(&line, 6).len(), 1);