GitHub connector: support subscribing and unsubscribing to issue notifications

Feature request

When GitHub is connected to ChatGPT/Codex, the connector should support managing the authenticated user's notification subscription for an existing GitHub issue.

Specifically, it should be possible to:

• determine whether the current user is subscribed to an issue;
• subscribe to an issue; and
• unsubscribe from an issue.

Motivation

The connector can read issues and perform several issue mutations, but it does not expose an operation for managing issue notification subscriptions.

For example, this request could not be completed through the connected GitHub account:

Subscribe me to openai/codex#26227 and openai/codex#36650.

The current workaround is to open GitHub manually or fall back to a local GitHub CLI/API workflow. Posting a comment is not an equivalent workaround because it changes the issue discussion and may notify other participants.

Expected behavior

With GitHub connected, ChatGPT/Codex should be able to:

1. read the current user's subscription state for one or more issues;
2. subscribe or unsubscribe the user as requested;
3. read back the resulting state; and
4. confirm the result without posting a comment or requiring the user to open GitHub manually.

Acceptance criteria

• The connector can query the current user's subscription state for an issue.
• The connector can subscribe the current user to an issue.
• The connector can unsubscribe the current user from an issue.
• The operations use the connected GitHub identity and permissions.
• Requests involving multiple issues can be completed and confirmed per issue.
• Subscription changes do not post comments or otherwise modify issue content.
• Unsupported or permission-denied operations return a clear, actionable error.

Related issues

• #17475 requests issue creation and a permission-upgrade flow for the GitHub connector. It establishes the broader need for ordinary GitHub mutations through the connector, but does not cover issue notification subscriptions.
• #37583 proposes a separate OpenAI-native feedback tracker with a conversational subscription operation; it does not add subscription support to the GitHub connector.
• #16159 concerns MCP resource-update subscriptions, not GitHub issue notifications.

I could not find an existing issue, discussion, or pull request that requests this specific GitHub connector capability.

No files or tests are named. Start by locating the GitHub connector and its existing issue-mutation operations, then trace how connected identity and permissions are handled; done means implementing per-issue subscription status, subscribe, unsubscribe, confirmation, and clear unsupported or permission-denied errors without posting comments.