Add reusable release-lifecycle workflow

[ellulpatrick]

Summary

• Adds a shared release-lifecycle.yml reusable workflow (workflow_call) for trunk-based repos
• Handles: Claude risk assessment, draft release upsert, Slack notification (linked text, permanent URLs, Buildkite links), and post-publish branch cleanup
• Each repo only needs a thin ~20-line caller — no more copy-pasting the full workflow

Usage

In each repo's .github/workflows/release-lifecycle.yml:

name: Release Lifecycle
on:
  push:
    branches: ['release/**']
  release:
    types: [published]
  workflow_dispatch:
jobs:
  release-lifecycle:
    uses: ordermentum/.github/.github/workflows/release-lifecycle.yml@main
    secrets:
      SLACK_BOT: \${{ secrets.SLACK_BOT }}
      CLAUDE_CODE_OAUTH_TOKEN: \${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}

Test plan

• Merge this PR
• Update Documentum to use the thin caller (PR #626)
• Cut a release branch and verify the full flow works end-to-end

🤖 Generated with Claude Code