HANDOFF.md: note 5-dot Arbeitstage indicator follow-up

Follow-up to 1aca417. Updates the §9 Phase 12 entry to describe the new
5-dot visual (green = active, gray = off, no labels, tooltip carries
the names), and appends both the UI tweak and the Phase-12-shipped
HANDOFF commit to §13's git history.

No code changes.

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

HANDOFF.md

@@ -259,14 +259,16 @@ with a `BOOTSTRAP_ADMIN` audit row.
       `data-href` + `app.js`; CSP dropped `'unsafe-inline'` and the
       Tailwind CDN host. Strict CSP now in effect.
 - [x] **Phase 12 — Per-week weekday selection (Mo–Fr) drives Arbeitstage**
-      (`a634582`): `sprint_weeks.active_days_mask` is the new source of
-      truth; `max_working_days` is a cached `popcount(mask)` projection.
-      Sprint Settings exposes five checkboxes (Mo Di Mi Do Fr) per week;
-      the sprint view's Arbeitstage header reads the derived count
-      read-only. `PATCH /sprints/{id}/week/{week_id}` now accepts
-      `active_days_mask` or `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).
+      (`a634582`, follow-up UI `1aca417`): `sprint_weeks.active_days_mask`
+      is the new source of truth; `max_working_days` is a cached
+      `popcount(mask)` projection. Sprint Settings exposes five checkboxes
+      (Mo Di Mi Do Fr) per week. The sprint view's Arbeitstage row shows
+      a row of five dots per week (green = active, gray = off) — no
+      labels, tooltip carries the day names. `PATCH
+      /sprints/{id}/week/{week_id}` now accepts `active_days_mask` or
+      `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).
 
 ### Upcoming
 
@@ -341,6 +343,8 @@ before acting — nothing here is load-bearing once it grows stale.
 ## 13. Git history (as of this handoff)
 
 ```
+1aca417 Sprint view Arbeitstage: 5-dot weekday indicator instead of a number
+59eb1d7 HANDOFF.md: mark Phase 12 shipped
 a634582 Phase 12: per-week weekday selection (Mo–Fr) drives Arbeitstage
 a1a1266 HANDOFF.md: mark Phases 8–11 shipped + codify the maintenance rule
 ab9430b Phase 11: vendor Tailwind + drop inline onclick + tighten CSP