ref(scm): Add quota policy for GitHub API requests

[cmanallen]

Certain referrers need reserved quota to ensure their requests are always completed. This pull request aims to enable that. This does not handle secondary rate-limits whose calculations are not publicly available.

To use the reserved quota system you must:

1. Register your referrer in the referrer allocation dictionary.
2. Use the with client.referrer(name): expression to scope your requests to your referrer.
   • Lower priority requests can be made outside the with block which falls back to the shared quota pool.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit ed77b82. Configure here.}