stale-card-sweeplisted

# stale-card-sweep — flag what a closing diff just made stale ## Why this exists A card is created for a defect. Before it is picked up, a different, larger card gets implemented and covers the same ground. The first card stays open. Nothing connects "this diff just landed" to "these open cards describe exactly what it fixed" — until someone happens to notice by eye and writes it down by hand. That noticing does not repeat reliably. Measured cost of the gap this skill closes: a pilot spawned on a card whose work had already shipped in an earlier commit produced an empty branch — ~209,000 tokens spent discovering, the hard way, that the card should have been flagged stale at the closure of the covering card. A `grep`-cheap mechanical check would have cost nothing. ## When to run this At the moment a card is about to move to its terminal "closed" list (`Done`/`NotDoing` on this project's board convention — adapt to whatever the tracker calls closed). Run it **before** the move, using the closing card's own diff. ## A second trigger: at COMMIT time, advisory and silent The mechanism above only ever fires at card CLOSURE. Work done outside any card — an inline instruction, done directly, closing nothing — never triggers it, and cards it just made obsolete stay open. `toolkit/scripts/git-hooks/post-commit-stale-card-sweep.sh` closes that gap: it runs the SAME layer-1 `sweep()` mechanism after every commit, opt-in (see the script's own header for the install step), silent un