external-pr-viabilitylisted

# External PR Viability Use this before writing a single line of code for an unsolicited PR against a repository you do not already have merged standing in. ## The problem A correct, fully-tested, contribution-guideline-compliant PR can be closed within seconds, with zero review and zero comment, even though CI passed. That is not a code-quality signal — a genuine quality rejection leaves a comment or a "changes requested" review, because the point of a comment is to get the author to fix something. A silent, near-instant close with passing checks means the PR was never evaluated on its merits: it was closed because of who opened it, not what was in it. No amount of correctness, test coverage, or contribution-guideline compliance changes that outcome, and reattempting on the same repo (a different issue, a rewritten description) wastes the same amount of effort again. Confirmed directly: a PR fixing a real, independently-verified one-line bug — with a red/green-tested regression test, a linked issue, a filled-in contribution template, and the required changelog entry — was closed by a core-team member 34 seconds after the final push. Checking the last 100 merged PRs on that repository showed every single author was either a core-team member or the dependency-update bot: zero outside contributors merged, ever, in that window. Other recent external PRs from unrelated contributors had received the identical silent treatment. ## Rule Before implementing a fix for an unsolic