Triaging contributions under the issue-link gate

FastMCP auto-closes external PRs unless the author is assigned to a referenced issue (see require-issue-link.yml). The practical effect: contributors open an issue, open a PR, get auto-closed, and ask to be assigned. The maintainer almost never sees the PR directly — the issue is the decision point, and assigning the author is the single action that reopens their PR and sends it into review.

This skill turns "look at this issue" into one of two outcomes:

• Assign — the issue is valid, we want it fixed, an external PR is appropriate, and a sound PR already exists → assign the author (auto-reopens the PR) and queue it for code review.
• Decline — leave the issue/PR closed and explain why on the issue.

Be opinionated about declining. The gate moved spam from junk PRs to junk issues; this skill is worthless if it just rubber-stamps assignment. Assignment is a commitment to review and likely merge, not a courtesy.

How the gate works (the part that matters here)