build: upgrade vite 8 + vitest 4.1, add prom-client (#124)

* build: add commitlint for structured commit message validation

* build: upgrade vite 8 + vitest 4.1, add prom-client as explicit dep

- Upgrade vite ^7.3.1 → ^8.0.0 and vitest ^4.0.18 → ^4.1.0
- Add prom-client ^15.1.3 as explicit dependency (was phantom dep
  that got de-hoisted when commitlint was added, causing silent
  server crash on startup)

Author: DivMode

commitlint.config.ts

@@ -0,0 +1,3 @@
+export default {
+  extends: ["@commitlint/config-conventional"],
+};

lefthook.yml

@@ -1,24 +1,7 @@
 commit-msg:
   commands:
-    conventional-commit:
-      run: |
-        MSG=$(grep -v '^#' "{1}" | head -1)
-        if [ -z "$MSG" ]; then exit 0; fi
-        PATTERN='^(feat|fix|docs|style|refactor|perf|test|build|ci|chore|revert)(\(.+\))?: .+'
-        if ! echo "$MSG" | grep -qE "$PATTERN"; then
-          echo ""
-          echo "  Bad commit message: $MSG"
-          echo ""
-          echo "  Must match: <type>(<scope>): <description>"
-          echo ""
-          echo "  Types: feat fix docs style refactor perf test build ci chore revert"
-          echo "  Examples:"
-          echo "    feat: add shadow DOM diagnostics"
-          echo "    fix(solver): resolve WS leak race"
-          echo "    chore: update dependencies"
-          echo ""
-          exit 1
-        fi
+    commitlint:
+      run: npx commitlint --edit {1}
 
 pre-push:
   commands: