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

hyperpolymath/a2ml-validate-action and k9-validate-action 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. Repos looked green
while the check had simply never run.

The actions moved rather than died:
  hyperpolymath/a2ml-ecosystem/validate-action
  hyperpolymath/k9-ecosystem/validate-action

Repointed, not vendored. The estate handover proposed vendoring the scripts into
every consumer; that would create one copy per repo to drift, which the same
document names as this estate's most recurring failure mode. Measured scope:
69 repos, 135 references -- not the ~272 estimated.

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

Verified: no dead refs remain, and every touched workflow still parses.

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

Author: hyperpolymath

.github/workflows/dogfood-gate.yml

@@ -39,7 +39,7 @@ jobs:
 
       - name: Validate A2ML manifests
         if: steps.detect.outputs.count > 0
-        uses: hyperpolymath/a2ml-validate-action@55e8c28bab4e7f2399fdbd57a6da1051369f3847 # main
+        uses: hyperpolymath/a2ml-ecosystem/validate-action@aa4b836bd969df2bc58128cb8e3d20bbc88d5e79 # main
         with:
           path: '.'
           strict: 'false'
@@ -87,7 +87,7 @@ jobs:
 
       - name: Validate K9 contracts
         if: steps.detect.outputs.k9_count > 0
-        uses: hyperpolymath/k9-validate-action@7c3c0e9fa5165626e74ecce78109b3295b798b92 # main
+        uses: hyperpolymath/k9-ecosystem/validate-action@89f3c2702f4f650a92aa7411502f38da06abd562 # main
         with:
           path: '.'
           strict: 'false'