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/tests/leader_pty_e2e/common.rs

@@ -26,12 +26,9 @@ pub(crate) const PROMPT: &str = "go";
 /// Response sentinel the mock server streams back.
 pub(crate) const MOCK_RESPONSE_SENTINEL: &str = "MOCKRESPONSE";
 
-/// Cold leader-client bring-up budget. History: 60s → 120s → 240s while these
-/// cases ran interleaved with the full `pty_e2e` suite (each leader case
-/// spawns multiple full pager processes; suite-wide contention pushed cold
-/// bring-up past two minutes). Now that the leader cases run in their own
-/// serialized target the budget can come back down after a green soak week —
-/// tracked in the leader test-infra plan.
+/// Cold leader-client bring-up budget, generous because each leader case
+/// spawns multiple full pager processes; can come back down after a green
+/// soak week — tracked in the leader test-infra plan.
 pub(crate) const LEADER_TIMEOUT: Duration = Duration::from_secs(240);
 
 /// Streamed-turn deadline in leader mode (same contention rationale).