fix(chat): CH6a/b rework — grip media, retail window-id model, floaty fixture

Applies docs/research/2026-08-10-ch6ab-review-findings.md in full:

- BLOCKER 1: UiResizeGrip now carries its ElementInfo/resolve pair and
  draws its own authored DirectState media (a synthetic parameterless
  grip still draws nothing, preserving existing resize-drag tests).
  DatWidgetFactory.BuildResizeGrip threads resolve through. All seven
  live grips on the main chat window now resolve a non-zero sprite,
  restoring the visible borders/corners CH6a silently dropped.

- SHOULD-FIX 2: ChatWindowState gains BroadcastTargetWindow, a sentinel
  distinct from every real window id (0-4), fixing the bug where the
  main window's explicit-addressing branch coincided with the broadcast
  check (both were literal 0). SetFilter's main-window no-op is dropped
  — the main window's filter is now genuinely settable. ChatWindowController
  .Bind takes a ChatWindowState (the same canonical instance the floating
  windows already share) and GetTranscriptLines builds a real accept
  predicate instead of accept:null. Verified safe: ClientLocal (0x1A)
  never reaches ChatLog (AddText routes it to the SpewBox and returns),
  so nothing observable regresses.

- SHOULD-FIX 3: UiButton.SuppressSelfToggle stops the four chat-window
  indicator buttons (DAT property 0x0B=true, no retail click handler)
  from flipping their own Selected mirror on a stray click.

- SHOULD-FIX 4: generated and committed chat_floaty_2100005b.json from
  the real installed dats; added the permanent RetailLayoutFixtureGenerator
  entry. All three flagged FloatingChatWindowController assumptions
  (input field, title bar, close button) are confirmed correct against
  real data — no controller code changes needed. New finding: unlike the
  main window, ALL EIGHT floaty border/corner elements are live Type-9
  grips (the floaty's own title bar is its move handle), so a floaty
  window resizes from every edge and corner.

- SHOULD-FIX 5: register row AP-189 documents the shared-500-entry/
  200-line-tail vs retail's per-window 10,000-line scrollback depth gap.

- NITs 1-5: documented the filter-persistence-only-on-/saveautoui
  asymmetry and the reconnect-preserves-filters intent; corrected the
  research doc's modifier-mask mislabel and the "ONLY function" false
  superlative; moved WrapText off ChatWindowController onto
  ChatTranscriptRenderer, closing the circular dependency.

Full Release suite: 12,420 passed / 4 skipped / 0 failed (baseline
12,392/4/0 at 22020ef2; net +28 tests, zero regressions).

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

src/AcDream.App/UI/RetailUiRuntime.cs

@@ -575,6 +575,17 @@ public sealed class RetailUiRuntime : IDisposable
     /// Capture the four floating windows' current text-type filters into
     /// the local settings store (research doc §4.4/§6.1 — local-only until
     /// CH6f's wire format). No-op when no store was wired.
+    ///
+    /// <para>
+    /// CH6a/b REJECT-review NIT 1: unlike window geometry/visibility (which
+    /// <see cref="_persistence"/> auto-saves on every change), a filter
+    /// change is only captured here — i.e. only when <see cref="SaveLayout"/>
+    /// runs, which today is exclusively the explicit <c>/saveautoui</c>
+    /// command. Harmless in practice (nothing currently mutates a window's
+    /// filter live — no options UI exists yet), but worth tightening to
+    /// auto-save-on-change once CH6e/CH6f gives filters a live settings
+    /// surface a user can actually edit mid-session.
+    /// </para>
     /// </summary>
     private void SaveChatWindowFilters()
     {
@@ -807,6 +818,7 @@ public sealed class RetailUiRuntime : IDisposable
             layout,
             _bindings.Chat.ViewModel,
             _bindings.Chat.CommandBus,
+            _bindings.Chat.Windows,
             _bindings.Assets.DefaultFont,
             _bindings.Assets.DebugFont,
             _bindings.Assets.ResolveSprite);