implement

/implement

Preflight: worktree guard

Task-scoped mutating skill — must run from a worktree, not the main checkout. Contract: skills/_shared/worktree-guard.md.

TOPLEVEL="$(git rev-parse --show-toplevel 2>/dev/null || echo '')"
if [ -z "$TOPLEVEL" ]; then
  echo "✗ worktree-guard: not inside a git repository" >&2
  exit 1
fi
BRANCH="$(git branch --show-current 2>/dev/null || echo '')"
DEFAULT_BRANCH="$(git symbolic-ref --short refs/remotes/origin/HEAD 2>/dev/null | sed 's@^origin/@@' || echo 'main')"
if [ -f "$TOPLEVEL/.forge/worktree-task.json" ]; then
  echo "✓ worktree-guard: $TOPLEVEL ($BRANCH)"
elif [ "$BRANCH" = "${DEFAULT_BRANCH:-main}" ]; then
  echo "✗ worktree-guard: refusing to run on default branch '$BRANCH' from $TOPLEVEL" >&2
  echo "  Parallel Claude Code sessions on the main checkout clobber each other's HEAD." >&2
  echo "  → cd into an existing worktree, or run /pickup-task to create one." >&2
  exit 1
else
  echo "⚠ worktree-guard: no .forge/worktree-task.json at $TOPLEVEL (branch: $BRANCH)" >&2
  echo "  Proceeding, but this worktree may be manually-created or stale." >&2
fi

Preconditions

• plans/tasks/{LINEAR-ID}.plan.md exists and was committed
• OR --quickfix flag with justification

Execution

1. Read plan
2. Execute step-by-step, committing after each logical unit
3. Use conventional commit messages
4. Mid-implementation forks: If a decision surfaces that wasn't in the plan, apply the fork severity filter from /plan-task (architectural / blast radius ≥ module / medium-high reversibility / changes next 3+ steps). If it qualifies, STOP and emit AskUserQuestion following skills/_shared/question-format.md. Do not auto-pick and document later — the user must see the fork before the code lands.
5. Record each surfaced question and its answer in the commit message body (single line: Decision: <fork> → <choice> per user answer) so the trail is visible in git history, not just the conversation.
6. Run npm run typecheck (or equivalent) after each major change