fix: always pass prompt via stdin to satisfy cagent exec's required prompt arg

[derekmisler]

Summary

Fixes a bug where cagent exec would fail when no prompt was provided, since the CLI requires a prompt argument. The action now always passes - (stdin) as the prompt argument, sending an empty string when no prompt is specified.

Changes

• action.yml: Unconditionally adds - to arguments and always pipes prompt via stdin (empty string if not provided), eliminating conditional branching for prompt handling
• review-pr/README.md: Removed redundant YAML example from documentation

Breaking Changes

None

How to Test

• Run the action without a prompt input and verify cagent exec executes successfully with an empty prompt
• Run the action with a prompt input and verify it still works as before

[derekmisler]

/describe

[docker-agent]

✅ PR description has been generated and updated!

[docker-agent]

Review Summary

✅ APPROVED - No new bugs introduced

The refactoring successfully achieves its goal of always passing a prompt via stdin to satisfy cagent exec's required prompt argument. The changes consolidate the conditional logic into a simpler, unconditional flow without introducing new functional issues.

Changes Reviewed

• ✅ Always adds - to ARGS to enable stdin input (line 498)
• ✅ Unconditionally pipes prompt (or empty string) to stdin
• ✅ Simplified branching logic while maintaining functional behavior
• ✅ README.md documentation cleanup

Optional Future Enhancement

While not blocking this PR, I noticed pre-existing exit code handling that could be improved in a future change:

• Line 512: EXIT_CODE=$? captures tee's exit code instead of the timeout command's exit code
• Line 518: EXIT_CODE=${PIPESTATUS[0]} captures printf's exit code instead of cagent's exit code

These issues existed before your changes and don't need to be addressed in this PR. The consolidation you've done is correct. Consider ${PIPESTATUS[1]} for proper exit code capture in both cases if you want to tackle this separately.

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Verdict: The changed code works correctly for its intended purpose. Ship it! 🚢