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

docs/adr/2719-emitted-artifact-attribution.md

@@ -120,7 +120,7 @@ A baseline-unavailable path must never be a bare `return`. In `node:test` that i
 ## Consequences
 
 - **Positive.** The conflict class ends rather than being automated around: 140 of 143 conflicted-file instances disappear. The propagation catch becomes a computed statement instead of a reviewer noticing an anomaly in hex. ~520 KB of committed derived state is deleted, along with the duplicate generator, `UPDATE_GOLDEN`, and `npm run gen:golden`. The artifact family finally has a name in `CONTEXT.md`.
-- **Negative — one-time migration.** Deleting the fixtures converts existing conflicts into delete/modify conflicts on the same 20 files, affecting 16 PRs. Verified by simulating the deletion with `git commit-tree` and re-running `git merge-tree`. The resolution is one identical command per PR and it is terminal; today's is regenerate-rebase-repush, recurring on every merge to `next`.
+- **Negative — one-time migration.** Deleting the fixtures converts existing conflicts into delete/modify conflicts on the same 20 files, affecting 16 PRs. Verified by simulating the deletion with `git commit-tree` and re-running `git merge-tree`. The resolution starts with one identical command per PR — `git rm tests/fixtures/golden-install-parity/*.json tests/workflow-size-baseline.json tests/agent-size-baseline.json` — and for a PR that changes no shipped file's size, that is the whole of it. **It is not terminal for a PR that grows a `gsd-core/workflows/*.md` or `agents/gsd-*.md` file**, which is the common case for a feature change: those need a second step, creating `tests/emitted-drift-ack.json` with an entry keyed on the **bare filename** (§3, §4). This ADR originally described the migration as terminal, full stop; that claim was corrected by #2778 after the Phase 4 cutover met it in the field on #2543. The failure output now states the second step itself, so the correction is discoverable where the contributor actually is rather than only here. Either way the cost is bounded and one-time; today's is regenerate-rebase-repush, recurring on every merge to `next`.
 - **Negative — new residual risks, accepted.** A provenance rule can map to the *wrong* source and still pass the totality guard: false attribution, not a false alarm. The Phase 3 dual-run window exists to surface exactly this, and spot-check tests on known pairs reduce it further. Separately, the relative chain holds only while the check runs on every merging PR — that is CI configuration rather than design, and if the selection rules narrow later it breaks silently.
 - **Neutral.** During Phase 1–3, github.com still reports `CONFLICTING`. Merge drivers live in `.git/config`, so forks lack them and GitHub's own merge never runs them. The driver removes the labour, not the label, and is retired in Phase 4.