HANDOFF.md: note stepper positioning + bounds-parsing hotfix

Annotates Phase 17 in §9 Shipped with hotfix `832b256` and a short
summary of the two bugs: (a) readBounds() read the IDL max property
which coerces a missing max to 0 via Number(""), so task-assignment
cells (min=0, no max) were clamped to [0, 0] — fixed by switching to
getAttribute + null/empty check so missing bounds report as NaN;
(b) popover horizontal anchor centred on the input's midpoint
instead of its left edge. SHA appended to §13 git history.

No code changes.

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

HANDOFF.md

@@ -422,7 +422,7 @@ with a `BOOTSTRAP_ADMIN` audit row.
       localStorage denial fallback).
 
 - [x] **Phase 17 — Hide native number spinners + custom 0.5-step
-      stepper popover** (`b457896`, UX tweak `c07af1c`). Three classes of number input —
+      stepper popover** (`b457896`, UX tweak `c07af1c`, hotfix `832b256`). Three classes of number input —
       day cells, RTB cells, task assignment cells — deal in half-day
       increments (or 0.05 for RTB). Browsers rendered each as
       `<input type="number">` with tiny native up/down spinner
@@ -488,7 +488,17 @@ with a `BOOTSTRAP_ADMIN` audit row.
       renders vertically (writing-mode: vertical-lr + direction:
       rtl, with slider-vertical / orient="vertical" fallbacks).
       Focus and pointerdown triggers remain for keyboard and
-      touch users respectively.
+      touch users respectively. **Hotfix `832b256`**: `readBounds()`
+      was using the IDL `boundInput.max` property which coerces a
+      missing `max` attribute to the empty string and then to 0 via
+      `Number("")` — the result was that task-assignment cells
+      (which set `min="0"` but have no `max`) were clamped to
+      `[0, 0]` and the +/− buttons appeared to do nothing on any
+      table but the Arbeitstage grid. Switched to `getAttribute()`
+      + explicit null/empty check so missing bounds report as `NaN`.
+      Same commit centres the popover on the input's horizontal
+      midpoint instead of aligning to its left edge — looks
+      balanced over narrow table cells.
 
 ### Upcoming
 
@@ -572,6 +582,8 @@ before acting — nothing here is load-bearing once it grows stale.
 ## 13. Git history (as of this handoff)
 
 ```
+832b256 Fix: stepper popover broken on task-assignment cells + not centred
+14a41b1 HANDOFF.md: note stepper hover + vertical-slider UX tweak on Phase 17
 c07af1c Stepper popover: hover-to-open + vertical range slider
 735aa4f HANDOFF.md: mark Phase 17 shipped
 b457896 Phase 17: hide native number spinners + custom 0.5-step stepper popover