A builder run that declines as "already done on main in <commit>" posts that note on its issue and stops further runs on it #6573

#6467 cost three runs, two of them a minute apart, each declining with "already done on main in 0e2eaaf4", and was parked as "the pull closed", which says nothing.

Done:

• [ ] When a build run ends with Declined: already done on main in <ids> and every id is on the base branch, the forge posts the "already done on main" note on the issue naming them, so a person or the planner can close it as done, and the issue is held from new build runs until someone acts.
• [ ] The park reason, when it is parked, quotes the decline rather than "the pull closed".
• [ ] An id not on the base is ignored, and the run is treated as today.
• [ ] Tests: a valid decline posts the note and holds the issue; an invalid id does not.

Files: the module that handles a build run's end in src/crew/, src/crew/parks.ts, a test.