fix(ci): bump a2ml-validate-action SHA to pick up contractile-shape fix

Picks up hyperpolymath/a2ml-validate-action#9 which fixes the validator's false-positive on contractile-shape .a2ml files (Trustfile, Intentfile, etc. using @directive: syntax). Was blocking every Dependabot PR in this repo with 'Missing required identity field'.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/dogfood-gate.yml

@@ -38,7 +38,7 @@ jobs:
 
       - name: Validate A2ML manifests
         if: steps.detect.outputs.count > 0
-        uses: hyperpolymath/a2ml-validate-action@b2f28c39491c0d1ff131b8fb9e197bfea79e411e # main
+        uses: hyperpolymath/a2ml-validate-action@fd7b2d840449568867f88cc93f64a9b3db1e2153 # main
         with:
           path: '.'
           strict: 'false'