fix(chat): CH6c review fixes — opaque default, opacity-transition register clauses

BLOCKER: ChatSettings.DefaultOpacity shipped retail's base ChatInterface
value (0.5) as ONE shared global default applied to every
RetailWindowManager-registered window, not just the four floating chat
windows retail itself fades. That faded the whole out-of-box registered
UI (radar, vitals, toolbar, main chat, ...) to 50% opacity, including
several windows that can never take keyboard focus and so were stuck at
0.5 permanently. Fixed to gmMainChatUI's 1.0/1.0 override
(0x004CD0F0) instead — retail-identical opaque presentation for the 11
non-chat windows and the main chat window; only the four floating chat
windows now diverge from retail's 0.5-while-idle default, and the
Settings -> Chat transparency slider remains fully user-settable.

AP-190 reworded and gains two new decomp-verified clauses: (3) retail
eases opacity toward its target by 5% of the delta per tick
(ChatInterface::ListenToGlobalMessage @0x004F3840, armed from the focus
element-messages at @0x004F5275) where acdream snaps -- deferred, needs
a UI frame-tick hook the opacity controller doesn't have; (4) retail's
focus predicate is the chat ENTRY FIELD specifically
(ChatInterface::IsTextEntryFocused @0x004F30A0) where acdream uses
any-focusable-descendant. Both findings + the pre-existing UiMenu.cs
PushAlphaAbsolute(1f) popup bypass are folded into the window-shell
research doc's opacity section.

NITs: fixed the stale "text bypasses the alpha" comment in
UiElement.DrawSelfAndChildren (CH6c already routed DrawStringDat/
DrawString through the same ApplyAlpha chokepoint as sprites/rects);
added RetailWindowManager.WindowUnregistered + wired
RetailWindowOpacityController to detach and forget a window unregistered
while it held focus (previously only Dispose detached, leaking any
window unregistered mid-focus for the rest of the session); added
post-Dispose no-op guards to the three Set* opacity mutators; added a
DrawString (BitmapFont path) alpha regression test and a DrawStringDat
outline/background-pass alpha test (the existing tests only ever
exercised the foreground/fill pass).

Also fixes RuntimeSettingsControllerTests.SettingsViewModelSavePreserves
SectionAndTargetOrder's now-stale "target-chat-opacity:0.5:1" expectation
(caught by the full-suite run this fix requires) to match the new 1.0
default.

Campaign ledger CH6c row updated to APPROVE-WITH-FIXES.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/research/2026-08-09-chat-retail-window-shell.md

@@ -503,15 +503,63 @@ than per-window: only a NEVER-SAVED option (a fresh character, nothing in the
 through, and even then only until the user's first slider drag pushes one
 shared value into every live window via `RecvNotice_GameplayOptionChanged`.
 
-acdream ships ONE shared global default — the base `ChatInterface` value,
-0.5/1.0 — applied uniformly to every window including the main chat window
-(register row AP-190 in `docs/architecture/retail-divergence-register.md`),
-rather than replicating `gmMainChatUI`'s per-class 1.0/1.0 override. The
+**CH6c review-fix round (2026-08-10): the shared default above was WRONG.**
+Shipping the base `ChatInterface` value (0.5/1.0) as ONE shared global
+default, combined with the scope extension to every registered window, faded
+the WHOLE registered UI (radar, vitals, toolbar, main chat, ...) to 50%
+opacity out of the box — including several windows that can never take
+keyboard focus at all, so they were stuck at 0.5 permanently. acdream now
+ships `gmMainChatUI`'s per-class 1.0/1.0 override (`0x004CD0F0`) as the
+shared global default instead (register row AP-190 in
+`docs/architecture/retail-divergence-register.md`), which is retail-identical
+for the 11 non-chat windows and the main chat window and leaves only the four
+floating chat windows diverging from retail's 0.5-while-idle fade — a
+default-VALUE divergence the transparency slider still fully covers. The
 linking invariant (active >= default, restored by dragging the OTHER value —
 verified from `SetDefaultOpacity`/`SetActiveOpacity`'s own bodies, matching
 the summary already recorded above) is ported exactly regardless of which
 default seeds it.
 
+### 3.1 Two more residuals found at the CH6c review (not yet ported)
+
+Both are decomp-verified and both are recorded as new AP-190 clauses; neither
+is implemented this round.
+
+**(a) Retail eases opacity between endpoints; acdream snaps.**
+`ChatInterface::ListenToGlobalMessage @0x004F3840` is the handler for global
+message id `3`, armed (`UIListener::RegisterForGlobalMessage(this, 3)`) from
+the element-focus messages `0x1A`/`0x1E`/`0x28`/`0x29`/`0x2E` inside the
+window's `ListenToElementMessage` switch at `0x004F5275`. Once armed, every
+tick nudges the live opacity toward whichever endpoint
+`IsTextEntryFocused` currently selects by 5% of the endpoint delta
+(`fabsl(target - current) * 0.05f`), and unregisters from the global message
+once the value lands within FP-epsilon of the target. acdream's
+`RetailWindowOpacityController.Apply` sets the target opacity directly on the
+focus-change event — the START and END states are retail-exact, but the
+transition is an instant snap instead of a roughly 20-tick fade. Porting the
+lerp needs a UI frame-tick hook `RetailWindowOpacityController` does not have
+today (it only reacts to `DescendantFocusChanged`); deferred.
+
+**(b) Retail's focus predicate is the chat entry field specifically; acdream's
+is any focusable descendant.** `ChatInterface::IsTextEntryFocused @0x004F30A0`
+tests `GetFocusDescendant(rootElement) == this->m_chatEntry` — literally the
+window's text-entry element, not "some descendant of this window has focus."
+acdream's `RetailWindowHandle.DescendantFocusChanged` (the event
+`RetailWindowOpacityController` subscribes to) fires whenever ANY focusable
+descendant of the window gains focus. For a window with exactly one
+focusable child the two predicates coincide; for a window with several (a
+settings panel's multiple controls, for example) acdream's broader predicate
+holds ActiveOpacity while retail would already have faded back to
+DefaultOpacity once focus left the specific text-entry widget.
+
+**Pre-existing, unrelated: `UiMenu.cs:293`'s opacity bypass.** Popup menus
+call `ctx.PushAlphaAbsolute(1f)` before drawing so a menu always reads solid
+even when it is opened from a translucent (faded) window — this is a
+deliberate acdream-only presentation choice (menus must stay legible
+regardless of the host window's current fade state), not a divergence from
+either of the two opacity mechanisms documented in this section, and it
+predates the CH6c slice.
+
 ---
 
 ## 4. Persistence — how filters, geometry, visibility and title survive