fix(ci): repoint the two DELETED validate-actions at the live ecosystem repos

dogfood-gate.yml pinned hyperpolymath/a2ml-validate-action and
hyperpolymath/k9-validate-action. Both repositories are DELETED (verified 404).
An unresolvable uses: ref produces NO check run at all -- not a red one -- so
'Validate A2ML manifests' and 'Validate K9 contracts' could never report, and
any ruleset requiring them was unsatisfiable. That is what blocked this very PR.

The actions were not lost, they MOVED:
  hyperpolymath/a2ml-ecosystem/validate-action  (action.yml verified at the pin)
  hyperpolymath/k9-ecosystem/validate-action    (action.yml verified at the pin)

Repointed rather than vendored. The estate handover proposed vendoring the
scripts into ~272 consumer repos; that would create 272 copies to drift, which
the same document names as this estate's most recurring failure mode. Repointing
is one line per file and keeps a single source.

SHAs are the ones already proven green in the-nash-equilibrium#83; both verified
to resolve (2026-07-25) and to contain validate-action/action.yml at that exact ref.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/dogfood-gate.yml

@@ -43,7 +43,7 @@ jobs:
 
       - name: Validate A2ML manifests
         if: steps.detect.outputs.count > 0
-        uses: hyperpolymath/a2ml-validate-action@05bcb78917c09702e90ed18004298a6728753914 # main
+        uses: hyperpolymath/a2ml-ecosystem/validate-action@aa4b836bd969df2bc58128cb8e3d20bbc88d5e79 # main
         with:
           path: '.'
           strict: 'false'
@@ -105,7 +105,7 @@ jobs:
 
       - name: Validate K9 contracts
         if: steps.detect.outputs.k9_count > 0
-        uses: hyperpolymath/k9-validate-action@bddcd9109ee96f9ea3fdb4bf51084fe9cd0909ce # main
+        uses: hyperpolymath/k9-ecosystem/validate-action@89f3c2702f4f650a92aa7411502f38da06abd562 # main
         with:
           path: '.'
           strict: 'false'