Add worktrees skill

.claude/skills/worktrees/SKILL.md

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+---
+name: worktrees
+description: |
+  Manage .worktrees/ lifecycle: create worktree, list worktrees, remove worktree,
+  clean worktrees, stale worktrees audit, isolate work, project clone.
+  TRIGGER when: any git worktree operation, branch isolation needed, stale worktrees
+  review, project clone under .worktrees/project/, worktree cleanup.
+allowed-tools: Bash
+---
+
+# Worktrees
+
+Manage `.worktrees/`. Full policy: `context/rules/git.md` § Worktrees.
+
+## DETECT BASE
+
+Run first. Every create op needs `$BASE`.
+
+```bash
+BASE=$(git show-ref --verify --quiet refs/heads/development && echo development || \
+       git show-ref --verify --quiet refs/heads/main && echo main || echo master)
+echo $BASE
+```
+
+## CREATE — new branch
+
+```bash
+PREFIX=feat   # feat bug task audit skill agent
+ISSUE=42
+DESC=short-desc
+BRANCH="$PREFIX/$ISSUE-$DESC"
+mkdir -p .worktrees
+git worktree add -b "$BRANCH" ".worktrees/$BRANCH" "$BASE"
+```
+
+## CREATE — existing branch
+
+```bash
+BRANCH=feat/42-short-desc
+mkdir -p .worktrees
+git worktree add ".worktrees/$BRANCH" "$BRANCH"
+```
+
+## LIST — all worktrees + age + PR status
+
+```bash
+git worktree list --porcelain | awk '/^worktree /{wt=$2} /^branch /{
+  sub("refs/heads/",""); br=$2; print wt, br}' | while read -r path branch; do
+  age=$(( ( $(date +%s) - $(git -C "$path" log -1 --format=%ct 2>/dev/null || echo $(date +%s)) ) / 86400 ))
+  pr=$(gh pr list --head "$branch" --state open --json number,title \
+       --jq '.[0] | if . then "#\(.number) \(.title)" else "no PR" end' 2>/dev/null)
+  printf "%-50s  %3dd  %s\n" "$branch" "$age" "$pr"
+done
+```
+
+## ISOLATE — in-flight work
+
+Main checkout has loose files. Don't stash. Don't switch.
+
+```bash
+# 1. Cut worktree off base
+BRANCH=feat/42-my-work
+git worktree add -b "$BRANCH" ".worktrees/$BRANCH" "$BASE"
+
+# 2. Copy files in
+cp path/to/file1 path/to/file2 ".worktrees/$BRANCH/<destination>/"
+
+# 3. Commit in worktree
+cd ".worktrees/$BRANCH"
+git add . && git commit -m "feat: ..."
+```
+
+Before cleaning main checkout — byte-check every file first:
+
+```bash
+for f in path/to/file1 path/to/file2; do
+  a=$(md5sum "$f" | awk '{print $1}')
+  b=$(git show "$BRANCH:$f" | md5sum | awk '{print $1}')
+  [ "$a" = "$b" ] && echo "same:  $f" || echo "DRIFT: $f"
+done
+```
+
+All `same:`? Then clean:
+
+```bash
+git restore path/to/file1 path/to/file2
+```
+
+Any `DRIFT:`? Stop. File not committed right. Fix first.
+
+## REMOVE — clean
+
+```bash
+BRANCH=feat/42-short-desc
+git worktree remove ".worktrees/$BRANCH"
+git worktree prune
+```
+
+Corrupted (not in `git worktree list`):
+
+```bash
+rm -rf ".worktrees/$BRANCH"
+git worktree prune
+```
+
+## STALE AUDIT — review only, no auto-delete
+
+List worktrees older than 30 days with no open PR. Surface. Don't remove.
+
+```bash
+git worktree list --porcelain | awk '/^worktree /{wt=$2} /^branch /{
+  sub("refs/heads/",""); br=$2; print wt, br}' | while read -r path branch; do
+  age=$(( ( $(date +%s) - $(git -C "$path" log -1 --format=%ct 2>/dev/null || echo $(date +%s)) ) / 86400 ))
+  [ "$age" -lt 30 ] && continue
+  pr=$(gh pr list --head "$branch" --state open --json number \
+       --jq 'length' 2>/dev/null)
+  [ "$pr" = "0" ] && printf "STALE %3dd  %s\n" "$age" "$branch"
+done
+```
+
+Review each `STALE` line. Remove manually if safe (see REMOVE above).
+
+## PROJECT CLONE
+
+Independent repo — not a harness branch. Has its own `.git`.
+
+```bash
+# Clone
+OWNER=ryaneggz
+REPO=some-project
+mkdir -p ".worktrees/project/$OWNER"
+git clone "https://github.com/$OWNER/$REPO.git" ".worktrees/project/$OWNER/$REPO"
+
+# Remove
+rm -rf ".worktrees/project/$OWNER/$REPO"
+```
+
+No `git worktree` for these. Plain `git clone` / `rm -rf`.