Add release automation workflow

[hdamker]

What type of PR is this?

enhancement/feature

What this PR does / why we need it:

Adds a complete release lifecycle workflow for CAMARA API repositories. The workflow automates:

• Release Issue management: auto-created from release-plan.yaml, tracks state via labels
• Snapshot creation: creates release branches with mechanically transformed API files
• Draft releases: auto-created when the Release PR is merged
• Publishing: final release publication with CHANGELOG and README updates

The workflow operates through slash commands (/create-snapshot, /discard-snapshot, /delete-draft, /publish-release) on Release Issues and uses a reusable workflow pattern — API repositories only need a lightweight caller workflow.

Components:

• Reusable GitHub Actions workflow (.github/workflows/release-automation-reusable.yml)
• Caller workflow template (release_automation/workflows/)
• 14 Python automation modules (release_automation/scripts/)
• 6 shared composite actions (shared-actions/)
• Mustache templates for bot messages, PR bodies, README sections, CHANGELOG
• Configuration for mechanical transformations (URL path rewrites per release type)
• Documentation: technical architecture, branching model, repository setup guide
• 471 unit tests (all passing)

Lifecycle: plan → snapshot → draft → publish, with state tracked via labels on the Release Issue and metadata in release-metadata.yaml.

Target branch: release-automation (parallel to main per the branching model — main continues to serve pr_validation v0 via the v0 tag).

Which issue(s) this PR fixes:

Related to camaraproject/ReleaseManagement#355

Special notes for reviewers:

• This PR targets the release-automation branch, not main. The two branches coexist per the branching model.
• All code is new — no modifications to existing pr_validation files on main.
• Squashed from 104 development commits on a fork branch.
• Test fixtures use hdamker/TestRepo-QoD as mock repository names — these are purely test data (all GitHub API calls are mocked).

Changelog input

release-note
Add release automation workflow for CAMARA API repositories

Additional documentation

docs
- [Technical Architecture](release_automation/docs/technical-architecture.md)
- [Branching Model](release_automation/docs/branching-model.md)
- [Repository Setup Guide](release_automation/docs/repository-setup.md)