Allow users with triage role or higher to archive pull requests [GA]

### Value Prop
Users with the triage role (and above) can now archive pull requests, giving repository maintainers the flexibility to delegate PR hygiene to trusted moderators without granting them write access to code. This aligns pull request archiving with the intended scope of the triage role — handling moderation tasks that don't modify source code. Teams managing large or open source repositories can distribute cleanup work more effectively across their contributors.

### Expected Outcome
By expanding archiving permissions to include triage, write, maintain, and admin roles, teams can reduce their reliance on write-level collaborators for routine PR housekeeping like closing spam or stale pull requests. This removes a friction point in open source and large-team workflows where trusted triagers were previously blocked from performing straightforward moderation tasks. The change brings the permission model in line with maintainer expectations and enables cleaner, faster PR management at scale.

No source file, test, or entry point is named. Start by reviewing the existing pull-request archiving permission model and the triage role's documented capabilities; done means triage, write, maintain, and admin users can archive pull requests without receiving code-modification access.

Vom Indexierungsmodell aus dem Issue-Text verfasst.