Add client-side rate limiting for pipeline execution

[sgardoll]

Summary

No debounce, throttle, or cooldown on pipeline execution beyond the isRunning boolean. Since all functions are exposed on window.*, programmatic invocation can burn through API credits rapidly.

Risk Assessment

• Risk Level: Medium
• Likelihood: Medium
• Impact: Medium — unexpected API costs
• Timeline: As user base grows

Suggested Fix

1. Add cooldown period (e.g., 3s) after pipeline completion before allowing re-run
2. Debounce the Run Pipeline button click handler
3. Optionally: add a usage counter in localStorage to warn users approaching high usage