fix(#1921): preserve verify-work state across gap-closure + defer follow-ups (#2025)

* fix(#1921): preserve verify-work state across gap-closure + defer follow-ups

Resuming /gsd:verify-work after /gsd:execute-phase --gaps-only lost the
verification state: UAT ## Gaps still read status: failed even after their
fix plans executed, so verify-work re-diagnosed them as fresh blockers,
spawned a new gap plan, and reported only the new plan verified. A new
state contract links each gap to its fix plan so fixed gaps are recognized.

- verify-work.md gap YAML: stable gap_id (G-{phase}-{N}) per gap.
- plan_gap_closure planner prompt: each *-PLAN.md tags the gap_ids it
  addresses in its frontmatter (gap_closure: true, gap_ids: [...]).
- new reconcile_gaps step (run at resume_from_file entry): marks a gap
  status: resolved when its plan has a matching *-SUMMARY.md — fixed gaps
  are not re-diagnosed and do not spawn new gap plans; a re-reported break
  is treated as a fresh regression with a new gap_id.
- deferred-follow-up branch: a future-work idea (signals: 'later',
  'next version', 'out of scope', ...) is captured to UAT ## Deferred
  Follow-Ups instead of becoming a blocking gap/plan.
- workflow-size baseline recaptured (verify-work LARGE tier, 38221/61440).

Closes #1921

* docs(#1921): backfill changeset pr 2025

* fix(#1921): balance <step> tags in verify-work.md via 4-backtick outer fence

The plan_gap_closure step nested a ```yaml example inside a ``` block;
same-length fences made stripFencedCode close the outer block early,
swallowing the step's </step> (14 opens / 13 closes). Widen the outer
fence to 4 backticks so the nested yaml is contained. Regenerate golden
fixtures + size baselines.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

tests/workflow-size-baseline.json

@@ -88,5 +88,5 @@
   "update.md": 20914,
   "validate-phase.md": 10789,
   "verify-phase.md": 40772,
-  "verify-work.md": 35215
+  "verify-work.md": 38267
 }