fix: recursively deploy built-in skill directories

[Yong-yuan-X]

Summary

Fixes #88.

deployBuiltinSkills previously copied only top-level files from each built-in skill directory. This caused team-wiki-codebase to be deployed without its nested references/ and scripts/ directories, leaving the skill incomplete after teamai pull.

This PR changes built-in skill deployment to recursively copy the full skill directory while skipping .-prefixed files/directories as suggested in #88.

It also updates ESM path resolution to use fileURLToPath(import.meta.url), which keeps the built-in skills path valid on Windows and remains correct on Linux/macOS.

Changes

• Recursively copy built-in skill directories during deployment.
• Skip .-prefixed files/directories during recursive copy.
• Add a regression test that verifies team-wiki-codebase deploys nested references/ and scripts/ files.
• Use fileURLToPath(import.meta.url) for cross-platform built-in skills path resolution.

Testing

• npx vitest run src/__tests__/skip-uninstalled-tools.test.ts
• npx tsc --noEmit
• npm run build
• git diff --check