Add semver-ci: commit-driven semantic versioning for Gitea Actions

Computes MAJOR.MINOR.PATCH.BUILD from NEW_MAJOR/NEW_MINOR/NEW_PATCH
whole-line tokens in commit messages since the last release tag.
Non-main branches get a BRANCH-SHORTSHA suffix and never release.
Maintains VERSION.md, writes $GITHUB_OUTPUT, and optionally creates
a Gitea release via API.

Includes spec, 67-assertion test, usage guide (docs/semver-ci.md),
and a drop-in Gitea Actions workflow template.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -24,6 +24,7 @@ This project uses **spec-driven development** (OpenSpec) as a testbed for agent-
 | `sync-repos` | Mirror git repos across remotes | Done |
 | `unreflected-logs` | Scan projects for unreflected session logs | Done |
 | `validate-skill` | Validate SKILL.md files against known Claude Code restrictions | Done |
+| `semver-ci` | Compute `MAJOR.MINOR.PATCH.BUILD` from commit-message tokens, maintain `VERSION.md`, and (on main) tag/push/create a Gitea release — see [`docs/semver-ci.md`](docs/semver-ci.md) and template at [`templates/gitea-workflow-version.yml`](templates/gitea-workflow-version.yml) | Done |
 
 ### Engagement modes (claude-profile)