A pure read groups the last 24 h of declined build runs by reason, so planning mistakes show as a count #6577

Runs this week declined because the work was already on main, or because it depended on a pull that had not landed (#6465, #6467, #6529). Each such decline is a planning mistake, and nothing counts them.

Done:

• [ ] New src/flow/declines.ts exports declines(rows, now), taking { issue, endedAt, summary }[] and returning, for the last 24 h, counts per reason: done_on_main (summary starts "Declined: already done on main"), not_on_main (names code or a pull not on main), off_direction, and other, each with up to 3 issue numbers.
• [ ] declinesSays(result) words it in one line, empty when there are none.
• [ ] Tests: each reason, the window edge, the cap of 3 numbers.

Files: src/flow/declines.ts, test/flow-declines.test.ts.

Before pushing: bun x tsc --noEmit and the new test.