chore: make agentic CI timeout configurable

[andreatgretel]

Summary

• Add an optional timeout_minutes input for manual agentic-ci-pr-review dispatches.
• Resolve the review job timeout from timeout_minutes, then AGENTIC_CI_TIMEOUT_MINUTES, then the existing 15 minute default.

Validation

• ruby -e 'require \"yaml\"; YAML.load_file(\".github/workflows/agentic-ci-pr-review.yml\"); puts \"yaml ok\"'
• git diff --check
• Commit hooks: trailing whitespace, end-of-file, YAML, large-file, merge-conflict, and line-ending checks passed; ruff hooks skipped because no Python files changed.

Canary result

Dispatched the branch workflow manually against PR #773 with timeout_minutes=30:

• Run: https://github.com/NVIDIA-NeMo/DataDesigner/actions/runs/28258692820
• Result: success
• gate: success
• review: success
• Pre-flight checks: success
• Run PR review recipe: success
• Post review comment: success
• Review job started at 2026-06-26T18:56:01Z and completed at 2026-06-26T19:05:04Z.
• Claude review step ran from 2026-06-26T18:56:16Z to 2026-06-26T19:04:56Z, about 9 minutes.

This confirms the configurable timeout path works from the PR branch. AWS Opus 4.8 completed the review within the 30 minute canary timeout.

Notes

After merge, set repo variable AGENTIC_CI_TIMEOUT_MINUTES=30 or 45 to make the increased timeout apply by default. Manual dispatches can still override the timeout with timeout_minutes.