HANDOFF.md: note stepper blur-close fix on Phase 17

Annotates Phase 17 in §9 Shipped with blur-fix `f189ef7` and its
behaviour: the popover now closes whenever focus leaves either the
bound input or a focusable element inside the popover, unless focus
is moving into another eligible number input (seamless rebind). The
Tab-specific keydown handler was replaced by the generic focusout
listener which is a proper superset. 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 slider popover
-      for number inputs** (`b457896`, UX tweak `c07af1c`, hotfix `832b256`, rewrite `15b2d24`). Three classes of number input —
+      for number inputs** (`b457896`, UX tweak `c07af1c`, hotfix `832b256`, rewrite `15b2d24`, blur-fix `f189ef7`). 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
@@ -517,6 +517,14 @@ with a `BOOTSTRAP_ADMIN` audit row.
       runs on every tick so Ressourcen / Available / ≤ reserves
       update smoothly during the drag. Escape, outside-pointerdown
       and Tab-out fallbacks remain for keyboard / touch paths.
+      **Blur-fix `f189ef7`** plugs a gap the rewrite left open: the
+      popover now closes whenever focus leaves either the bound input
+      or a focusable element inside the popover, unless focus is
+      moving into another eligible number input (seamless rebind, no
+      flicker). Catches the case where a click elsewhere blurred
+      the input but never landed on a registered "outside" target.
+      Replaces the Tab-specific keydown handler, which is now a
+      subset of the generic focusout behaviour.
 
 ### Upcoming
 
@@ -600,6 +608,8 @@ before acting — nothing here is load-bearing once it grows stale.
 ## 13. Git history (as of this handoff)
 
 ```
+f189ef7 Fix: stepper popover now closes when the bound input loses focus
+27eea76 HANDOFF.md: note slider-only stepper rewrite on Phase 17
 15b2d24 Stepper popover: slider-only, click-to-open, close on leave-popup
 515f9ec HANDOFF.md: note stepper positioning + bounds-parsing hotfix
 832b256 Fix: stepper popover broken on task-assignment cells + not centred