ci: add commitlint and Husky for conventional commit validation (#2416)

- Add @commitlint/cli and @commitlint/config-conventional at repo root
- Configure commitlint with project-specific types (security, etc.)
- Set up Husky v9 with commit-msg hook running commitlint
- Add pre-commit hook running biome check on CLI source

Fixes #2406

Agent: code-health

Co-authored-by: B <6723574+louisgv@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

commitlint.config.ts

@@ -0,0 +1,23 @@
+export default {
+  extends: ["@commitlint/config-conventional"],
+  rules: {
+    "type-enum": [
+      2,
+      "always",
+      [
+        "build",
+        "chore",
+        "ci",
+        "docs",
+        "feat",
+        "fix",
+        "perf",
+        "refactor",
+        "revert",
+        "security",
+        "style",
+        "test",
+      ],
+    ],
+  },
+};