HANDOFF.md: note buildTaskRow data-col hotfix on Phase 13

Appends the hotfix SHA (23ab365) to the Phase 13 entry in §9 with a
one-sentence explanation: buildTaskRow was missing the data-col
attribute that both the Phase 10 Columns dropdown and the Phase 13
focus auto-hide rely on, and that gap is now closed. §13 git history
gets 23ab365 plus the two missing HANDOFF commits (d0fdf53, e23cfac)
so the block matches `git log`.

No code changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

HANDOFF.md

@@ -269,7 +269,7 @@ with a `BOOTSTRAP_ADMIN` audit row.
       `active_days`; `max_working_days` in the body is rejected. Migration
       002 backfills legacy rows (half-days round up, clamped to 0..5).
       +14 tests, 88 total (was 74).
-- [x] **Phase 13 — Focus filter + Reset in the task list** (`b027c5d`):
+- [x] **Phase 13 — Focus filter + Reset in the task list** (`b027c5d`, hotfix `23ab365`):
       new `[data-focus-select]` in the task-list toolbar picks one sprint
       worker; `applyFilters()` grows a fourth AND predicate hiding rows
       whose `[data-assign][data-sw-id="{focus}"]` is not > 0, and a new
@@ -283,7 +283,10 @@ with a `BOOTSTRAP_ADMIN` audit row.
       (`sp:{sprintId}:focusWorker` joins the existing namespace). Pure
       client-side; no schema, route, or audit changes. Tests unchanged
       at 88 (the phase is 100% JS over existing HTML, same pattern as
-      Phase 10).
+      Phase 10). Hotfix `23ab365` stamps `data-col` on JS-built task
+      cells in `buildTaskRow`, which was a pre-existing gap exposed by
+      both the Columns dropdown (Phase 10) and this phase's focus
+      auto-hide — new-task cells are now recognised by both systems.
 
 ### Upcoming
 
@@ -361,7 +364,10 @@ before acting — nothing here is load-bearing once it grows stale.
 ## 13. Git history (as of this handoff)
 
 ```
+23ab365 Fix: stamp data-col on JS-built task row cells
+d0fdf53 HANDOFF.md: mark Phase 13 shipped
 b027c5d Phase 13: Focus filter + Reset in the task list
+e23cfac HANDOFF.md: add Phase 13 plan (Focus filter + reset)
 815e232 HANDOFF.md: note 5-dot Arbeitstage indicator follow-up
 1aca417 Sprint view Arbeitstage: 5-dot weekday indicator instead of a number
 59eb1d7 HANDOFF.md: mark Phase 12 shipped