fix: address Copilot review round 4

- Reword the CI guarantee in AGENTS.md, docs/quality-gate.md and the
  pre-push-gate skill: a green gate means every check CI applies has
  passed here — the strongest predictor of green CI, not a proof — and
  name the residual (a test that passes only when slowed) as #1596's
  class to fix rather than headroom to keep.
- docs/quality-gate.md: cli's validate DID build, through `test`'s
  `pretest` hook; say that the build goes with the dropped `test` leg and
  `coverage:cli` builds once, later — in both places.
- Update the two source comments that still described `local:gate` as
  running `validate` (verify-skills.mjs, verify-build-gate.mjs).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PsmUAZ6aLUAFqenjJKSSRp
Signed-off-by: cliffhall <cliff@futurescale.com>

scripts/verify-build-gate.mjs

@@ -350,8 +350,9 @@ if (!output.includes(ERROR_PREFIX)) {
 // so PROBE_MODULE must appear. Without this, a repo that already leaks a built-in
 // would report OK even if the probe was tree-shaken or entryPath went stale —
 // branch (c)'s failure, silently inverted into a pass. (Unreachable inside
-// `npm run local:gate`: `validate`'s `build:web` fails first on a pre-existing leak — but
-// this script is a documented standalone command, run exactly when debugging one.)
+// `npm run local:gate`: web's `check` — its `build`, run by `local:validate` —
+// fails first on a pre-existing leak; but this script is a documented
+// standalone command, run exactly when debugging one.)
 if (!output.includes(PROBE_MODULE)) {
   fail(
     `the #1769 gate fired, but ${PROBE_MODULE} isn't among the offenders — it ` +

scripts/verify-skills.mjs

@@ -330,7 +330,7 @@ function main(argv = process.argv.slice(2)) {
   // The authoritative parse, when it is available — strictly a bonus, and only
   // from the EXACT pinned CLI.
   //
-  // `local:gate` runs `validate` (and therefore this) before the pinned
+  // `local:gate` runs `local:validate` (and therefore this) before the pinned
   // `verify:skills:cli` step, so a local CLI on any other version could reject
   // skills that CI's pinned validator accepts — and the gate would exit here,
   // never reaching the reproducible step (Copilot). Accepting merely "new enough"