An issues list finds the open pulls that close its rows from their numbers and bodies alone, not 200 whole pulls #6397

Later: The repository is FLOW ONLY until the #5930 alarms stay clear for 24 h, and this is a read-path speed-up.

Replaces #6324. Pull #6341 built it, and two reviews judged the code sound: the SELECT joins pull, the newest pull still wins, and the no-numbers path holds. It was refused only for being off the FLOW ONLY direction. When flow is clear, rebuild it from pull #6341's branch on a fresh main.

Done: as #6324. openPullsClosing (src/core/pulls.ts) reads number, body of open pulls in one SELECT and hydrates only the pulls that close a number on the page. A test asserts 3 pulls are hydrated, not 150, and asserts nothing on the clock. The pull pastes closing;dur= from its preview, before and after.