docs(plans): record S22 rows 10, 12, 14 and fix the drift-line unit

What this records

This MR fills three rows of the Status table in docs/plans/2026-08-04-s22-storage-accounting.md.

Row	Step	MR
10	drain triggers and fan-out	!1751 (merged)
12	repository-level size_bytes recompute	!1712 (merged)
14	reconciliation task	!1757 (merged)

Row 12 was already empty before step 14 opened its MR. !1712 (merged) merged on 2026-08-19. One batch MR clears that older gap and the new row together.

The other empty rows stay empty. Steps 15, 17, 18 and 19 have no MR, open or merged.

Why it is separate

This is a batch tracking MR, not a step MR. The Status rows land here instead of in !1751 (merged) and !1757 (merged), by operator direction. No step number goes in the title, because this MR implements no step.

One correction to the plan text

Step 14 of the plan said "one structured log line per drifting scope", in two places. The task writes one line per drifting counter column. The field list in the same sentence is singular, with one counter column, one persisted value and one reconciled value. A scope that drifts in both of its columns has no shape it can take in one line. The spec side of the same correction is in docs/specs/S22-storage-accounting.md, on the !1757 (merged) branch.

This is a bot message 🤖 — /smurfit