feat: add parallel issue implementation capability with worktrees

Add complete capability set for orchestrating parallel issue implementation
with automated review cycles using git worktrees.

Components:
- worktrees skill: Git worktree patterns + bundled scripts for reliable operations
- spawn-issues skill: Event-driven orchestrator (Haiku) for parallel workflow
- issue-worker agent: Implements issues autonomously (Sonnet)
- code-reviewer agent: Reviews PRs with quality checks (Haiku, read-only)
- pr-fixer agent: Addresses review feedback automatically (Haiku)

Workflow: /spawn-issues creates worktrees → spawns workers → reviews PRs →
fixes feedback → iterates until approved → cleans up worktrees

Scripts handle error-prone worktree operations. Orchestrator uses event-driven
approach with task notifications for efficient parallel execution.

Co-Authored-By: Claude Code <noreply@anthropic.com>

skills/worktrees/scripts/create-worktree.sh

@@ -0,0 +1,74 @@
+#!/bin/bash
+set -euo pipefail
+
+# Create a git worktree for issue work or PR review
+#
+# Usage:
+#   ./create-worktree.sh issue <issue-number>
+#   ./create-worktree.sh review <pr-number> <branch-name>
+#
+# Returns: Absolute path to created worktree (stdout)
+
+MODE="$1"
+REPO_PATH=$(git rev-parse --show-toplevel 2>/dev/null || pwd)
+REPO_NAME=$(basename "$REPO_PATH")
+WORKTREES_DIR="${REPO_PATH}/../worktrees"
+
+# Ensure worktrees directory exists
+mkdir -p "$WORKTREES_DIR"
+
+# Fetch latest from origin
+cd "$REPO_PATH"
+git fetch origin >/dev/null 2>&1
+
+case "$MODE" in
+  issue)
+    ISSUE_NUMBER="$2"
+    WORKTREE_NAME="${REPO_NAME}-issue-${ISSUE_NUMBER}"
+    WORKTREE_PATH="${WORKTREES_DIR}/${WORKTREE_NAME}"
+
+    # Get issue title for branch name
+    ISSUE_TITLE=$(tea issues "$ISSUE_NUMBER" 2>/dev/null | grep -i "title" | head -1 | cut -d: -f2- | xargs || echo "untitled")
+
+    # Create safe branch name
+    BRANCH_NAME="issue-${ISSUE_NUMBER}-$(echo "$ISSUE_TITLE" | tr '[:upper:]' '[:lower:]' | tr ' ' '-' | tr -cd '[:alnum:]-' | cut -c1-50)"
+
+    # Remove worktree if it already exists
+    if [ -d "$WORKTREE_PATH" ]; then
+      git worktree remove "$WORKTREE_PATH" --force 2>/dev/null || true
+    fi
+
+    # Delete branch if it exists
+    git branch -D "$BRANCH_NAME" 2>/dev/null || true
+
+    # Create worktree with new branch from main
+    git worktree add "$WORKTREE_PATH" -b "$BRANCH_NAME" origin/main >/dev/null 2>&1
+
+    echo "$WORKTREE_PATH"
+    ;;
+
+  review)
+    PR_NUMBER="$2"
+    BRANCH_NAME="$3"
+    WORKTREE_NAME="${REPO_NAME}-review-${PR_NUMBER}"
+    WORKTREE_PATH="${WORKTREES_DIR}/${WORKTREE_NAME}"
+
+    # Remove worktree if it already exists
+    if [ -d "$WORKTREE_PATH" ]; then
+      git worktree remove "$WORKTREE_PATH" --force 2>/dev/null || true
+    fi
+
+    # Create worktree from existing branch
+    git worktree add "$WORKTREE_PATH" "origin/${BRANCH_NAME}" >/dev/null 2>&1
+
+    echo "$WORKTREE_PATH"
+    ;;
+
+  *)
+    echo "Error: Invalid mode '$MODE'. Use 'issue' or 'review'" >&2
+    echo "Usage:" >&2
+    echo "  $0 issue <issue-number>" >&2
+    echo "  $0 review <pr-number> <branch-name>" >&2
+    exit 1
+    ;;
+esac