fix: tsci push should find fallback file when no entrypoint

[64johnlee]

Summary

Fix Issue #2797 - tsci push fails when no index.circuit.tsx file and no mainEntrypoint

Problem: tsci push would fail with "No entrypoint found" error, while tsci dev would find a fallback file.

Solution: When no entrypoint is found, tsci push now searches for any .tsx, .ts, or .circuit.json file as a fallback (similar to how tsci dev works).

Testing

bun test tests/cli/push/

Closes #2797

[github-actions]

This PR has been automatically marked as stale because it has had no recent activity. It will be closed if no further activity occurs.