Convert release automation to a GitHub Agentic Workflow

[Copilot]

The repository had a hand-written release.yml; this changes release automation to the same agentic workflow model used elsewhere in the repo. The new release flow creates workflow-asset releases from a compiled agentic source and prepends concise release highlights.

• Release workflow source

  • Adds .github/workflows/release.md as the canonical release workflow definition
  • Removes the hand-written .github/workflows/release.yml
  • Commits the compiled .github/workflows/release.lock.yml

• Release behavior

  • Keeps the release entrypoint manual with tag and target inputs
  • Compiles both repository workflows and published workflows/ assets before release creation
  • Fails if generated workflow artifacts are out of date
  • Publishes the workflow source and lock files as release assets

• Agent-generated release notes

  • Adds an agent prompt that gathers release context after creation
  • Uses the update-release safe output to prepend a short 🌟 Release Highlights section to the generated notes

• CI alignment

  • Updates CI to compile both .github/workflows and workflows/
  • Marks .github/workflows/*.lock.yml as generated in .gitattributes, matching the existing treatment for published lockfiles

safe-outputs:
  update-release:

jobs:
  release:
    steps:
      - name: Compile repository workflows
        run: gh aw compile

      - name: Compile published workflows
        run: gh aw compile --dir workflows