chore: add pre-commit hook for Ruff lint and frontend tests

- Runs Ruff on staged .py files, blocks commit on lint errors
- Runs vitest on staged .ts/.tsx files, blocks commit on test failures
- Gracefully skips if ruff or node_modules not available
- Auto-installs via npm prepare script
- Shareable hook in scripts/pre-commit

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -8,7 +8,8 @@
     "dev:frontend": "cd frontend && npm run dev",
     "dev:backend": "python main.py",
     "build": "cd frontend && npm run build",
-    "start": "npm run build && python main.py"
+    "start": "npm run build && python main.py",
+    "prepare": "cp scripts/pre-commit .git/hooks/pre-commit 2>/dev/null && chmod +x .git/hooks/pre-commit 2>/dev/null || true"
   },
   "devDependencies": {
     "concurrently": "^9.0.0"

scripts/pre-commit

@@ -0,0 +1,44 @@
+#!/bin/sh
+# Pre-commit hook: runs Ruff on staged Python files and frontend tests on staged TS/TSX files
+#
+# Install: cp scripts/pre-commit .git/hooks/pre-commit && chmod +x .git/hooks/pre-commit
+
+set -e
+
+# Colors
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[0;33m'
+NC='\033[0m'
+
+# --- Ruff lint on staged Python files ---
+STAGED_PY=$(git diff --cached --name-only --diff-filter=ACM -- '*.py')
+
+if [ -n "$STAGED_PY" ]; then
+    printf "${YELLOW}Running Ruff on staged Python files...${NC}\n"
+    if command -v ruff >/dev/null 2>&1; then
+        if ! echo "$STAGED_PY" | xargs ruff check; then
+            printf "${RED}Ruff found issues. Fix them or run 'ruff check --fix' then re-stage.${NC}\n"
+            exit 1
+        fi
+        printf "${GREEN}Ruff passed.${NC}\n"
+    else
+        printf "${YELLOW}Ruff not installed, skipping Python lint. Install with: pip install ruff${NC}\n"
+    fi
+fi
+
+# --- Frontend tests on staged TS/TSX files ---
+STAGED_FE=$(git diff --cached --name-only --diff-filter=ACM -- 'frontend/src/**/*.ts' 'frontend/src/**/*.tsx')
+
+if [ -n "$STAGED_FE" ]; then
+    printf "${YELLOW}Running frontend tests...${NC}\n"
+    if [ -d "frontend/node_modules" ]; then
+        if ! (cd frontend && npx vitest run --reporter=dot 2>&1); then
+            printf "${RED}Frontend tests failed. Fix them before committing.${NC}\n"
+            exit 1
+        fi
+        printf "${GREEN}Frontend tests passed.${NC}\n"
+    else
+        printf "${YELLOW}frontend/node_modules not found, skipping tests. Run: cd frontend && npm install${NC}\n"
+    fi
+fi