enhance(#2778): make the size-ratchet failure name its own remedy (#2780)

* fix(#2778): exempt intentionally-absent paths from the glossary gate

check-glossary-refs asserts that every backticked tests/ token in
CONTEXT.md resolves on disk. tests/emitted-drift-ack.json (ADR-2719
section 3) is absent on a healthy next BY DESIGN — it appears only
inside a PR that needs it, which is what makes touching it the alarm.

It passed before only by accident of backtick pairing: CONTEXT.md's
RULESET entries are themselves backtick-wrapped and contain backticks,
so the token happened to fall outside a code span. Any edit that
shifted the parity exposed it. A gate that passes by luck is not
passing.

The exemption is exact, not a prefix hole: a sibling missing tests/
path still fails, and a test locks that.

* feat(#2778): make the size-ratchet failure name its own remedy

The growth branch stated a requirement and withheld the means of
satisfying it: no ack file named, no schema, no key format, and no
do-not-regenerate line — so the likeliest guess was to hunt for a
baseline that #2724 deleted. Observed live on #2543.

All remediation now comes from one frozen REMEDIATION export whose
example document is rendered from ACK_VERSION, so the taught schema
cannot drift from the schema parseAck accepts. A round-trip test feeds
the printed document back through parseAck.

The report is now built as a typed IR (buildReport) that formatReport
renders, so tests assert on structure rather than prose, per
CONTRIBUTING.md's raw-text-matching rule.

Two defects found and fixed inline while building:
- diffEmitted's validation early-return omitted newFileCapExceeded
  while formatReport reads its length, so the branch that reports a
  failed git diff threw a TypeError instead of naming the problem.
- Printing one complete ack document per failing branch made each read
  as the whole file, so pasting the second over the first silently lost
  an acknowledgment. One document now covers the whole report.

Closes #2778

* chore(#2778): backfill changeset pr number to 2780

CONTRIBUTING.md

@@ -780,6 +780,17 @@ its exact byte delta and needs the same acknowledgment; the outer tier hard caps
 `tests/workflow-size-budget.test.cjs` / `tests/agent-size-budget.test.cjs` are unaffected
 and still apply.
 
+You do not need to memorize any of this. **The failure output names its own remedy** — it
+tells you the file to create, that it does not exist yet, which key to use, and prints a
+minimal valid document you can paste. Note the two key spaces, because the message says
+which one applies: an unattributable **hash** ripple is keyed on the emitted path
+(`skills/gsd-add-tests/SKILL.md`), while **growth** is keyed on the bare filename as it
+appears under `gsd-core/workflows/` or `agents/` (`explore.md`). When you remove the last
+entry from `tests/emitted-drift-ack.json`, delete the file too — its presence is the
+alarm, so an empty one signals nothing. Nothing here is regenerated: if you find yourself
+looking for a baseline file to re-run a generator over, that file was deleted by #2724 and
+is not coming back.
+
 `npm run regen:derived` still exists for the artifacts that ARE committed and derived —
 `sync-manifest-versions`, the ADR index, the capability matrix, the inventory manifest,
 the registry, and `tests/fixtures/install-tree/*.json` (`npm run gen:install-tree`, the