fix(ui): spell-bar drag-reorder works — the per-frame rebuild was destroying the dragged cell (#354)

Everything already existed — the drag payloads, the favorite wire pair
(0x1E3 add-at-position / 0x1E4 remove, byte-confirmed against retail's
Event_AddSpellFavorite @0x006A0F70 and ACE), the insert-shift state
ops. The bug: lifting a favorite fires SpellbookChanged, the next
per-frame Tick rebuilt the bar, the rebuild flushed and recreated
every cell, and UiRoot's subtree-removal safety net canceled the
in-flight drag whose source had just been destroyed — one frame after
every lift, before any drop could land.

The rebuild now defers for the duration of the drag gesture, and the
drop ports retail's own -1-if-lifted-before-target index adjustment
(SpellCastSubMenu::AddFavorite @0x004C7060) so final positions are
byte-identical: insert-shift, not swap; drag-out still deletes (the
lift's removal stands on a missed drop, retail's shape). The
real-pointer-pipeline test fails against the pre-fix code with the
exact cancellation and passes after; a discriminator pins that
physical-item drop handlers reject the spell payload.

AP-172 files the one presentation divergence (mid-drag reflow happens
on release, not continuously) — renumbered from the agent's AP-171
draft, which collided with the same-day double-click row. #354 filed
and closed.

Clean-room complete solution: 11,541 passed / 4 skipped / 0 failed.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/ISSUES.md

@@ -24,6 +24,42 @@ What does NOT go here:
 - Every session: scan OPEN issues at start; promote/close anything we touched during the session before ending.
 - Promoting to a Phase: mark as `DONE (promoted to Phase X)` + commit SHA where the Phase entry landed.
 
+## #354 — Spell-bar drag reorder did not work: lifting a favorite canceled the drag before the drop could land
+
+**Status:** CLOSED 2026-08-08 — user gate finding ("I should be able to
+rearrange spells on the spell bar. Like dragging one out and dropping it
+in another position. That does not work today"), diagnosed and fixed same
+session. Root cause: `SpellcastingUiController.BeginFavoriteDrag` performs
+retail's press-time removal (`gmSpellcastingUI::RecvNotice_ItemListBeginDrag`
+@0x004C7360 → `RemoveSpellFromMenu`, matching `PlayerModule::RemoveSpellFavorite`
+@0x005D4910) — correct and pre-existing — but that removal fires
+`SpellbookChanged`, and the very next per-frame `Tick()` (production drives
+this unconditionally via `RetailUiRuntime.Tick`) called `Rebuild()`, which
+flushes and recreates every favorite-bar cell (`UiItemList.Flush` →
+`RemoveChild`). `UiRoot`'s subtree-removal safety net
+(`ClearSubtreeOwnership`) cancels any drag whose source widget is
+destroyed — so the drag was silently canceled one frame after every lift,
+before the user could complete a drop. Empirically confirmed: a real-pointer-
+path test (`DragFavoriteOntoAnotherSlot_ThroughTheRealPointerPipeline_ReordersAndSyncsWire`)
+driving `UiRoot.OnMouseDown`/`OnMouseMove`/a mid-drag `Tick`/`OnMouseUp` fails
+with `screen.DragSource == null` against the pre-fix code, and passes after
+it. Fix (`SpellcastingUiController.cs`): defer the favorite-list rebuild for
+the whole drag gesture (`_favoriteDragActive`), and compensate the drop-time
+target index for the resulting stale sibling numbering by porting retail's
+own `SpellCastSubMenu::AddFavorite` @0x004C7060 index adjustment (decrement
+the target by one when the lifted item's original index was before it) —
+same insert-shift semantics `PlayerModule::AddSpellFavorite` @0x005D43E0's
+`InsertPos` already implements, now reachable through a live drag. Recorded
+as AP-172 in the divergence register (the mid-drag visual reflow now happens
+on release rather than continuously, final positions/wire are retail-exact).
+Tests: `SpellcastingUiControllerTests.cs` (the real-pointer-path reorder
+test + a payload-discriminator sabotage check confirming a spell-favorite
+payload is rejected by a physical `IItemListDragHandler`), `SpellbookTests.cs`
+(`SetFavorite`/`RemoveFavorite` insert-shift unit coverage). Wire golden
+bytes for `AddSpellFavorite`/`RemoveSpellFavorite` (opcodes 0x1E3/0x1E4) and
+`RuntimeCharacterState.TryAddFavorite`/`TryRemoveFavorite` were already
+covered and needed no change.
+
 ## #353 — Toolbar selected-object text: count field ignores authored HJustify; name field does not wrap to its authored two lines
 
 **Status:** CLOSED 2026-08-08 — user-passed ("Ok slider bar looks ok!" + the wrap confirmed); the OneLine routing fix (4cfcc8b3) completed it. (RightAligned on the authored HJustify=2 entry; two stacked centered one-line labels wrapping at the authored 140 px via WrapNameTwoLines).