plans: DEFERRED gains row 307 N1 (row 270's store-unreadable doesn't stick; #1814 landed d243f6b25)

docs/plans/DEFERRED.md

@@ -655,3 +655,12 @@ Open follow-up (Huey's BUILD.md, sage-3357), to become a row. Row 272 (#1777) la
 ## Row270 N6 rebound: the ledger and the session.list read are still unbounded after 272
 
 Row 272 (#1777) lands without bounding the compaction ledger or the whole-file read on session.list, and it records no reason the 64 MiB collection cap is enough. N6 above stays open. It moves to the row after 307 (#1814, Vikunja 598), because 307 reshapes the compaction reading in packages/seat/src/compactions.mjs and both rows would edit readLedger. That row bounds the ledger or the read, with a test and a mutant, or records why the cap is enough.
+
+## Row307 N1: row 270's store-unreadable doesn't stick
+
+Duckworth, row 307 build round 1 (duckworth-0285, note d43690d0b). When a collection finds an unreadable
+session store header, it writes store-unreadable. The cursor then moves past the bad header, so the next
+collection never checks it again and the count reads as known with 0. The row 307 ledger test pins this
+behavior as it stands, so the move didn't change it. Bound to a follow-up row on row 270's
+store-unreadable path. The fix keeps the unreadable state until the header reads clean, or re-checks the
+header on every collection. Either way it's an old-test change and goes to Mos.