M4a task 14: post's comment was now_ms's; fixed, and every comment read

A script that rewrote the skeleton's comments put `now_ms`'s text on `post`. Task 14's second
session saw the contradiction and deliberated until cut off. Both comments are fixed, each
todo!() comment in tasks 14 and 15 was read beside its signature, and both tasks now say to stop
and quote a comment that does not fit. Lesson T29.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/plans/M4a/14-gatewayd-serve.md

@@ -107,6 +107,8 @@ never set.
 
 ## Stop and report if
 
+- A comment above a `todo!()` does not fit its function, or contradicts a test. The comments were
+  written by hand and one was wrong before; stop at once and quote it, rather than guess.
 - A test passes only sometimes, or a test takes 5 s or more (that is a wait that timed out, not a
   pass).
 - A written function (`run`, `connect`, `Gateway::new`, `event_loop`, `catch_up`) seems to need a