feat: enforce issue-linked branches + document versioning/tagging policy (#48)

Formalize the branch↔issue relationship and add a release/version-tagging policy.

Branch/issue linkage:
- scripts/worktree-start now validates branch names: implementation branches
  must match (fix|feat|docs|chore)/issue-<number>-<slug>; review branches
  review/pr-<number>-<slug>. Untraceable names are rejected with a clear error
  (exit 2). New --allow-unlinked override for genuine exceptions. --dry-run
  preserved.
- Documented issue → branch → worktree → PR → cleanup traceability in the
  runbook and the portable SKILL, including the claim-comment convention and
  Closes #n / Refs #n PR-body usage.
- Noted that Gitea exposes no native issue→branch API field (only a PR head
  branch), so linkage is enforced via branch name + claim comment + PR body +
  cleanup.

Versioning / tagging policy (docs only; no release automation yet):
- SemVer vMAJOR.MINOR.PATCH (v0.x.y while unstable) with PATCH/MINOR/MAJOR bump
  rules.
- Annotated tags only, from the exact commit on remote master, only after the
  full suite passes, with release notes referencing merged PRs/issues. Never tag
  feature branches, dirty worktrees, unreviewed/self-authored work, or commits
  not on remote master.
- Release runbook in the runbook + SKILL, plus a new
  skills/llm-project-workflow/templates/release-tag.md prompt template.

Tests: worktree-start branch validation — accepts fix/feat/docs/chore/issue-*
and review/pr-*, rejects fix/random-name / my-branch / non-numeric issue,
honors --allow-unlinked, preserves --dry-run. Full suite 291 passed / 0 failures;
bash -n clean; git diff --check clean; no secrets.

Release-tag automation (a scripts/release-tag helper) intentionally deferred to a
later issue to keep this diff narrow and testable.

Closes #48. Refs #38, #39, #46.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/llm-workflow-runbooks.md

@@ -180,6 +180,24 @@ under `branches/`. The main repository checkout is an orchestration checkout:
 use it for status checks, issue creation/claiming, and creating worktrees, but
 do not edit tracked repository files there.
 
+**Issue → branch → worktree → PR → cleanup.** Every implementation branch is
+tied to an issue number so the work is traceable end to end:
+
+| Stage | Form |
+|-------|------|
+| Issue | `#123` (claimed with `status:in-progress`) |
+| Branch | `(fix\|feat\|docs\|chore)/issue-123-<slug>` (review: `review/pr-456-<slug>`) |
+| Worktree | `branches/fix-issue-123-<slug>` (slashes → hyphens) |
+| PR | body says `Closes #123` (closes) or `Refs #123` (related) |
+| Cleanup | remove remote+local branch + worktree folder; drop `status:in-progress` |
+
+`scripts/worktree-start` **rejects** implementation branches that are not
+issue-linked (use `--allow-unlinked` only for genuine exceptions). When claiming,
+post a comment like
+`Claimed. Branch: fix/issue-123-<slug>. Worktree: branches/fix-issue-123-<slug>.`
+Gitea has no native issue→branch API field (only a PR's head branch), so this
+linkage is enforced by branch name + claim comment + PR body + cleanup.
+
 Branch folders are ignored by git via `branches/`, so dirty work in one issue
 does not block starting an unrelated issue in a separate branch folder. No LLM
 may edit another issue's branch folder unless explicitly assigned to that issue.
@@ -319,6 +337,32 @@ All mutating attempts — allowed, blocked, failed, or succeeded — are audit-l
 with the profile and authenticated user when `GITEA_AUDIT_LOG` is set (see
 [`safety-model.md`](safety-model.md)).
 
+## Releases and version tags
+
+Versions follow SemVer — **`vMAJOR.MINOR.PATCH`**, using **`v0.x.y`** while
+unstable. Pick the bump by the largest change since the last tag:
+
+- **PATCH** — bug fixes, docs, tests, wrappers, non-breaking workflow polish.
+- **MINOR** — new MCP tools, new workflow helpers, new config features;
+  backward-compatible behavior.
+- **MAJOR** — breaking config/schema/API behavior or a changed MCP contract.
+
+Tags are **annotated** (`git tag -a`), created **only from the exact commit on
+remote `master`**, **only after the full suite passes**, and carry release notes
+referencing the merged PRs/issues. **Never tag** feature branches, dirty
+worktrees, unreviewed or self-authored work, or commits not on remote `master`.
+
+Release runbook (see [`../skills/llm-project-workflow/templates/release-tag.md`](../skills/llm-project-workflow/templates/release-tag.md)):
+
+1. `git fetch prgs --prune`.
+2. Confirm local `master` equals `prgs/master` (`0	0`) and the tree is clean.
+3. Run the full test suite; stop on failure.
+4. Review merged issues/PRs since the last tag
+   (`git log --oneline <last-tag>..prgs/master`).
+5. Choose the version bump.
+6. `git tag -a <vX.Y.Z> prgs/master -m "<notes referencing #issues / PRs>"`.
+7. `git push prgs <vX.Y.Z>`; add release notes if the forge supports it.
+
 ## Safety notes
 
 - Never place raw tokens or passwords in any LLM MCP config; reference secrets