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-tui/src/app/dispatch/tests/settings.rs

@@ -126,10 +126,10 @@ fn toggle_vim_mode_propagates_to_open_subagent_views() {
     );
 }
 /// `/vim-mode` must toggle vim from the DASHBOARD too (not just an
-/// agent view) — previously it early-returned unless an agent was
-/// active, so it was a silent no-op and the overview's j/k never
-/// turned on. Turning vim ON also focuses the overview so j/k
-/// navigate immediately; turning it OFF returns focus to the input.
+/// agent view) — an early return without an active agent would make
+/// this a silent no-op and the overview's j/k would never turn on.
+/// Turning vim ON also focuses the overview so j/k navigate
+/// immediately; turning it OFF returns focus to the input.
 #[serial_test::serial(KIGI_AGENT_DASHBOARD)]
 #[test]
 fn toggle_vim_mode_works_on_dashboard_and_focuses_overview() {
@@ -776,11 +776,9 @@ fn refresh_open_settings_modals_updates_reset_confirm_settings_state() {
         _ => panic!("expected ResetSettingsConfirm still active"),
     }
 }
-/// The
-/// dispatch-arm bail-out path is verified directly via
-/// `#[should_panic]` in debug mode rather than the previous
-/// `if cfg!(debug_assertions) { return; }` placebo which gave
-/// debug-mode CI no coverage of the routing-bug bail-out.
+/// The dispatch-arm bail-out path is verified directly via
+/// `#[should_panic]` in debug mode, giving debug-mode CI real
+/// coverage of the routing-bug bail-out.
 #[test]
 #[cfg(debug_assertions)]
 #[should_panic(expected = "OpenResetConfirm dispatched without an open Settings modal")]