fix(#1478,#1479,#1480): prohibit ungrounded baselines, error-suppressing fallbacks, and stale-artifact authority in planner verify blocks (#1482)

* fix(#1478,#1479,#1480): prohibit ungrounded baselines, error-suppressing fallbacks, and stale-artifact authority in verify blocks

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore: add changeset for #1478/#1479/#1480 planner verify gate fix

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: correct changeset format

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(#1478,#1479,#1480): fix test contract violations from new planner dimensions

gsd-planner.md exceeded both the planner-decomposition 48K char limit and
the reachability-check 50K char limit after the new HARD RULE blocks were
added inline. The full rule details already exist in planner-antipatterns.md
(added in the same PR); replace the verbose inline blocks with a single
@-reference pointer to the antipatterns file, reducing the file from 50981
to 49130 chars (under both limits).

Also regenerate tests/agent-size-baseline.json to reflect the new sizes of
gsd-planner.md and gsd-plan-checker.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/agent-size-baseline.json

@@ -22,8 +22,8 @@
   "gsd-nyquist-auditor.md": 7255,
   "gsd-pattern-mapper.md": 12487,
   "gsd-phase-researcher.md": 40638,
-  "gsd-plan-checker.md": 42003,
-  "gsd-planner.md": 49216,
+  "gsd-plan-checker.md": 44646,
+  "gsd-planner.md": 49306,
   "gsd-project-researcher.md": 22014,
   "gsd-research-synthesizer.md": 13653,
   "gsd-roadmapper.md": 21781,