fix: add package-lock.json for CI support

Remove package-lock.json from .gitignore and commit lock file.
CI workflow uses npm ci which requires a lock file, and
actions/setup-node cache: npm requires it for cache keys.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bmadcode

.gitignore

@@ -4,7 +4,6 @@ pnpm-lock.yaml
 bun.lock
 deno.lock
 pnpm-workspace.yaml
-package-lock.json
 
 test-output/*
 coverage/