ci: vendor validation scripts and remove remote action pins

[hyperpolymath]

Automated PR to fix CI after deleted actions.

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Summary by Gitar

• CI Workflows:
  • Vendored validation scripts for A2ML and K9 into .githooks/
  • Removed remote action pins from dogfood-gate.yml in favor of local script execution

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[gitar-bot]

Code Review ✅ Approved

Vendored validation scripts for A2ML and K9 into .githooks and removed remote action pins from dogfood-gate.yml to run locally. No issues found.

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