Adopt ACM v1.1 PR governance in alt-asset-spec

[Copilot]

This PR aligns alt-asset-spec with the ACM standard by introducing PR-level boundary contracts and automated governance checks. It adds the minimum repository scaffolding needed to require and validate ACM content in pull requests.

• PR governance template

  • Adds .github/PULL_REQUEST_TEMPLATE.md with:
    • required <!-- ACM-START --> ... <!-- ACM-END --> block
    • ACM v1.1 typed contracts and distributed primitives
    • reviewer sign-off checklist for unsupported/unknown boundaries and evidence verification

• CI governance gate

  • Adds .github/workflows/acm-governance.yml to run on PR open/edit/sync/reopen
  • Validates PR body ACM content via @roblarsen/acm-cli
  • Posts/updates a governance audit comment and fails the workflow on invalid or missing ACM

• Local workflow alignment

  • Updates package.json with:
    • acm:validate:file
    • acm:validate:pr-body
  • Ensures contributors can run the same ACM checks locally as CI

• Contributor and agent documentation

  • Updates README.md to document ACM-required PR descriptions and governance gate behavior
  • Updates llm.md to require ACM v1.1 contract output for implementation/refactor work

{
  "scripts": {
    "acm:validate:file": "npx --yes @roblarsen/acm-cli validate --file",
    "acm:validate:pr-body": "npx --yes @roblarsen/acm-cli validate --pr-body"
  }
}

[roblarsen]

👍