HANDOFF.md: note buildTaskRow owner-dropdown hotfix on Phase 10

Annotates Phase 10 in §9 Shipped with hotfix `7c298d3` and a
two-sentence summary of the regression: the phase's toolbar refactor
from <select> to checkbox multi-filter left ownerChoices() in
sprint-planner.js reading a selector that no longer existed, so every
client-built task row had an empty owner dropdown until a reload
re-rendered it server-side. Affects both /sprints/{id} and the Phase
15 /sprints/{id}/present view since they share the toolbar markup.
SHA appended to §13 git history.

No code changes.

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

HANDOFF.md

@@ -252,9 +252,17 @@ with a `BOOTSTRAP_ADMIN` audit row.
       /users/{id}` with self-demote and last-admin guardrails. Pure static
       `UserController::demoteGuardrail` is testable with no PDO/session
       setup. +6 tests.
-- [x] **Phase 10 — Task list polish** (`c35a934`): multi-select owner
-      filter (checkbox dropdown) and column-visibility toggle, both
-      pure client-side with localStorage persistence per sprint.
+- [x] **Phase 10 — Task list polish** (`c35a934`, hotfix `7c298d3`):
+      multi-select owner filter (checkbox dropdown) and column-visibility
+      toggle, both pure client-side with localStorage persistence per
+      sprint. Hotfix `7c298d3` repairs a regression `c35a934` left in
+      `sprint-planner.js`: `ownerChoices()` still scraped the pre-Phase-10
+      `[data-owner-filter] option` selector (replaced by
+      `[data-owner-filter-opt]` checkboxes in this phase), so every
+      client-built task row (admin clicks "+ Add task") had an empty
+      owner dropdown until a page reload re-rendered it server-side.
+      Also affects the Phase 15 `/sprints/{id}/present` view since it
+      reuses the same toolbar markup + JS.
 - [x] **Phase 11 — CSP hardening** (`ab9430b`): vendored Tailwind via
       a Node css-builder Docker stage; inline onclick replaced by
       `data-href` + `app.js`; CSP dropped `'unsafe-inline'` and the
@@ -426,6 +434,8 @@ before acting — nothing here is load-bearing once it grows stale.
 ## 13. Git history (as of this handoff)
 
 ```
+7c298d3 Fix: buildTaskRow owner dropdown was empty until a page refresh
+c70e442 HANDOFF.md: mark Phase 15 shipped
 d1dda4f Phase 15: big-screen (beamer) task viewer at /sprints/{id}/present
 48c56b7 HANDOFF.md: add Phase 15 plan (big-screen task viewer)
 d59120c HANDOFF.md: mark Phase 14 shipped