feat: implement unified HaLOS versioning and release system

[mairas]

Overview

Implement the unified HaLOS versioning and release system as documented in cockpit-apt PRs #97 and #99.

Reference Implementation

• cockpit-apt PR #97: feat: implement unified HaLOS versioning and release system halos-org/cockpit-apt#97 - Unified versioning system
• cockpit-apt PR #99: fix(ci): use underscore in git tags per DEP-14 standard halos-org/cockpit-apt#99 - DEP-14 compliance
• container-packaging-tools issue #63: feat: implement unified HaLOS versioning and release system halos-org/container-packaging-tools#63

Implementation

Follow the same approach as container-packaging-tools (see issue #63 for detailed checklist).

Key Changes

1. Create .github/scripts/ with calculate-revision.sh, generate-changelog.sh, test-version-handling.sh
2. Update .github/workflows/main.yml and release.yml
3. Add bumpversion command to ./run script
4. Update AGENTS.md with version management documentation

Version System

• VERSION file: Upstream version only (e.g., 0.2.0)
• Git tags: v{upstream}+{N}_pre (unstable), v{upstream}+{N} (stable)
• Debian packages: {upstream}-{N}
• Auto-incrementing N based on git tags
• Same .deb for both channels

Benefits

✅ Auto-incrementing revisions
✅ Monotonic version ordering
✅ Git-compliant tags (DEP-14)
✅ Fixes missing .deb on draft releases

Implementation Checklist

MANDATORY: Follow halos-distro/docs/IMPLEMENTATION_CHECKLIST.md during implementation.

See container-packaging-tools issue #63 for complete checklist.

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