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-tools/src/reminders/lsp_diagnostics.rs

@@ -26,8 +26,8 @@ impl Reminder for LspDiagnosticsReminder {
 
         lsp.ensure_started_background();
 
-        // After SearchReplace edits, notify LSP so diagnostics refresh.
-        // The adapter routes immediately when ready and buffers pre-ready edits otherwise.
+        // Notify LSP of the edit so diagnostics refresh; when the adapter is not
+        // yet ready the notification is buffered rather than dropped.
         if let ToolOutput::SearchReplace(SearchReplaceOutput::EditsApplied(edits)) = tool_output
             && let Ok(content) = std::fs::read_to_string(&edits.absolute_path)
         {
@@ -35,7 +35,7 @@ impl Reminder for LspDiagnosticsReminder {
                 .await;
         }
 
-        // Drain any pending diagnostics (from this or previous edits).
+        // Drain diagnostics queued by this or earlier edits.
         if let Some(summary) = lsp
             .drain_diagnostics(std::time::Duration::from_millis(500))
             .await