fix(cli): fall back to Bun CLI JS

[jkoelker]

Platform packages can be skipped in CI, which leaves the wrapper without a binary to execute. Run the bundled CLI via Bun when binary resolution fails so install still works.

---

Summary by cubic

Add a Bun-based fallback to run the bundled JS CLI when the platform binary isn’t available. This keeps installs working in CI and preserves expected exit behavior.

• Bug Fixes
  • Runs dist/cli/index.js via Bun if binary resolution fails.
  • Preserves exit codes and handles SIGTERM/SIGKILL/SIGINT.
  • Clear guidance: install the platform package or Bun for the JS fallback.
  • Added getFallbackCliPath and a unit test.

^{Written for commit 176b4a5. Summary will update on new commits.}

[kdcokenny]

appreciate the pr but we need to properly package it up by enabling platform package publishing #829