fix(ci): repoint the deleted validate-actions at the live ecosystem repos (#297)

`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. The repo looked green while the check had simply
never run.

The actions **moved**: `a2ml-ecosystem/validate-action` and
`k9-ecosystem/validate-action`. Repointed rather than vendored —
vendoring would create one drifting copy per repo.

Measured scope: **69 repos, 135 references**. SHAs are those already
proven green in `the-nash-equilibrium#83`.

**Verified:** no dead refs remain; every touched workflow still parses.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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'