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/UiResizeGrip.cs

@@ -1,3 +1,7 @@
+using System;
+using System.Numerics;
+using AcDream.App.UI.Layout;
+
 namespace AcDream.App.UI;
 
 /// <summary>
@@ -23,10 +27,19 @@ namespace AcDream.App.UI;
 /// </para>
 ///
 /// <para>
-/// A grip is a small (5px) leaf with no children and no authored background
-/// media beyond its own cursor-feedback sprite; it exists purely as a precise
-/// hit region. <see cref="AcDream.App.UI.UiRoot"/> gives a directly-hit grip's
-/// own <see cref="Edges"/> priority over the generic proximity-based
+/// A grip is a small (5px) leaf with no children; it exists primarily as a
+/// precise hit region, but it IS authored with real border/corner media (the
+/// <c>0x06006129</c>-family sprites — CH6a/b REJECT-review BLOCKER 1,
+/// <c>docs/research/2026-08-10-ch6ab-review-findings.md</c>: every one of the
+/// seven live grips on the main chat window carries a non-zero DirectState
+/// sprite, and drawing nothing left the window with only its 400×5 top strip
+/// visible). A factory-built grip (<see cref="AcDream.App.UI.Layout.DatWidgetFactory.Create"/>,
+/// Type 9) therefore draws its own DirectState media exactly like
+/// <see cref="AcDream.App.UI.Layout.UiDatElement"/> would; a synthetic grip
+/// built with the parameterless constructor (unit tests exercising only the
+/// resize-drag behavior) carries no media and draws nothing, matching its
+/// prior behavior. <see cref="AcDream.App.UI.UiRoot"/> gives a directly-hit
+/// grip's own <see cref="Edges"/> priority over the generic proximity-based
 /// <see cref="AcDream.App.UI.UiRoot.HitEdges"/> heuristic, so e.g. the chat
 /// window's top-left/top-right CORNER grips resize (including the Y/top axis)
 /// while the plain top EDGE strip in between remains a pure move handle.
@@ -34,6 +47,57 @@ namespace AcDream.App.UI;
 /// </summary>
 public sealed class UiResizeGrip : UiElement
 {
+    private readonly ElementInfo? _info;
+    private readonly Func<uint, (uint tex, int w, int h)>? _resolve;
+
+    /// <summary>Synthetic grip with no authored media — used by unit tests that
+    /// exercise only the resize-drag hit-testing/edge behavior.</summary>
+    public UiResizeGrip()
+    {
+    }
+
+    /// <summary>
+    /// Factory-built grip (CH6a/b REJECT-review BLOCKER 1): carries its resolved
+    /// <see cref="ElementInfo"/> and sprite resolver so it draws its own
+    /// authored DirectState media, the same way every other dat-imported leaf
+    /// does. <see cref="UiElement.ClickThrough"/> is left at the base
+    /// <see langword="false"/> default — unlike <see cref="UiDatElement"/>'s
+    /// decoration default of <see langword="true"/> — because a grip must stay
+    /// hit-testable to capture the resize drag.
+    /// </summary>
+    public UiResizeGrip(ElementInfo info, Func<uint, (uint tex, int w, int h)> resolve)
+    {
+        _info = info;
+        _resolve = resolve;
+    }
+
+    /// <summary>
+    /// This grip's authored DirectState sprite file id (0 for a synthetic grip,
+    /// or an authored grip with no media). Exposed for conformance tests —
+    /// BLOCKER 1's regression guard is that every one of the seven live Type-9
+    /// grips resolves a non-zero value here.
+    /// </summary>
+    public uint SpriteFile => _info is not null && _info.StateMedia.TryGetValue("", out var media)
+        ? media.File
+        : 0u;
+
+    /// <summary>
+    /// Draws this grip's own DirectState media exactly like
+    /// <see cref="UiDatElement.OnDraw"/> — tiled at native size (Normal), same
+    /// blend for Overlay/Alphablend since the sprite shader already
+    /// alpha-blends. A synthetic (parameterless-constructed) grip has no
+    /// resolver and draws nothing, matching its pre-BLOCKER-1 behavior.
+    /// </summary>
+    protected override void OnDraw(UiRenderContext ctx)
+    {
+        if (_resolve is null) return;
+        uint file = SpriteFile;
+        if (file == 0u) return;
+        var (tex, tw, th) = _resolve(file);
+        if (tex == 0 || tw == 0 || th == 0) return;
+        ctx.DrawSprite(tex, 0, 0, Width, Height, 0, 0, Width / tw, Height / th, Vector4.One);
+    }
+
     /// <summary>Retail <c>BorderLocation</c> (<c>acclient.h:4327</c>):
     /// <c>BORDER_NONE=0, BORDER_UL=1, BORDER_TOP=2, BORDER_UR=3, BORDER_RIGHT=4,
     /// BORDER_LR=5, BORDER_BOTTOM=6, BORDER_LL=7, BORDER_LEFT=8</c>.</summary>