fix: update ANTIGRAVITY_USER_AGENTS to working versions (1.14.x-1.15.x)

- Update User-Agent versions from blocked range (1.10.8-1.11.5) to working range (1.14.0-1.15.8)
- Align with ANTIGRAVITY_VERSIONS in src/plugin/fingerprint.ts
- Bump package version to 1.4.1