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>

scripts/worktree-start

@@ -3,21 +3,32 @@ set -euo pipefail
 
 usage() {
   cat <<'EOF'
-usage: scripts/worktree-start [--dry-run] <branch-name> [start-ref]
+usage: scripts/worktree-start [--dry-run] [--allow-unlinked] <branch-name> [start-ref]
 
-Create an issue-specific git worktree under branches/<branch-name-with-slashes-replaced>.
+Create an issue-linked git worktree under branches/<branch-name-with-slashes-replaced>.
+
+Branch names must be traceable to an issue (or a PR, for review branches):
+  implementation: (fix|feat|docs|chore)/issue-<number>-<short-description>
+  review:         review/pr-<number>-<short-description>
+Use --allow-unlinked to bypass the check (discouraged).
 
 Examples:
   scripts/worktree-start fix/issue-123-example
-  scripts/worktree-start --dry-run review/pr-123-scope-check prgs/master
+  scripts/worktree-start --dry-run review/pr-456-scope-check prgs/master
 EOF
 }
 
 dry_run=0
-if [[ "${1:-}" == "--dry-run" ]]; then
-  dry_run=1
+allow_unlinked=0
+while [[ "${1:-}" == --* ]]; do
+  case "$1" in
+    --dry-run) dry_run=1 ;;
+    --allow-unlinked) allow_unlinked=1 ;;
+    --help) usage; exit 0 ;;
+    *) usage >&2; exit 2 ;;
+  esac
   shift
-fi
+done
 
 if [[ $# -lt 1 || $# -gt 2 ]]; then
   usage >&2
@@ -27,6 +38,26 @@ fi
 branch="$1"
 start_ref="${2:-prgs/master}"
 
+# Enforce issue-linked, traceable branch names (issue → branch → worktree → PR).
+if [[ "$allow_unlinked" -eq 0 ]]; then
+  if [[ "$branch" =~ ^(fix|feat|docs|chore)/issue-[0-9]+-.+ ]] \
+     || [[ "$branch" =~ ^review/pr-[0-9]+-.+ ]]; then
+    :
+  else
+    cat >&2 <<EOF
+Untraceable branch name: $branch
+
+Implementation branches must be issue-linked:
+  (fix|feat|docs|chore)/issue-<number>-<short-description>
+Review branches:
+  review/pr-<number>-<short-description>
+
+Fix the branch name, or pass --allow-unlinked to override (discouraged).
+EOF
+    exit 2
+  fi
+fi
+
 script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 repo_root="$(cd "$script_dir/.." && pwd)"
 worktree_name="${branch//\//-}"