feat: add issue auto-assignment, CSAT survey, and stale workflow management

[rshashank17]

Summary

This PR introduces automated issue lifecycle management workflows for antigravity-cli:

1. Auto-Assignment Workflow (auto-assignment.yml & auto-assignment.js):
   • Automatically assigns newly opened issues to repository maintainers on a round-robin rotation.
2. CSAT Survey Workflow (csat.yml & csat.js):
   • Triggers when an issue is closed. If tagged with any supported component/category label, it posts an automated Customer Satisfaction (CSAT) survey link prefilled with the issue URL.
3. Stale Issue & PR Management (stale.yml):
   • Runs a daily scheduled check to mark inactive items labeled stat:awaiting response as stale after 7 days (14 days for PRs), and automatically closes them if no response is received.

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Changes Included

• .github/workflows/auto-assignment.yml
• .github/workflows/csat.yml
• .github/workflows/stale.yml
• .github/workflows/scripts/auto-assignment.js
• .github/workflows/scripts/csat.js

Steps to Clear (STC)

1. Test Auto-Assignment

1. Open a new test issue in the repository.
2. Verify that the workflow automatically assigns the issue to the maintainer (manirajc).

2. Test CSAT Survey

1. Open a test issue and apply a supported label (e.g., bug, documentation, question, or support).
2. Close the issue.
3. Verify that an automated comment is posted: "Are you satisfied with the resolution of your issue? [Yes] [No]".
4. Click Yes or No and verify that it opens the pre-filled Google Form with the correct issue URL.

3. Test Stale Bot

1. Confirm stale.yml is scheduled for 01:30 UTC daily.
2. Label an issue with stat:awaiting response.
3. Verify that after 7 days of inactivity, the bot marks it stale, and closes it after 7 additional days.