feat(D.2b): write-mode movement gate that preserves autorun

In chat write mode the keyboard belongs to the input — typing "swd" must not
walk the character — but AUTORUN must keep going (the user can chat while
running).

- InputDispatcher.IsActionHeld now returns false while WantCaptureKeyboard is
  set (a focused chat input), the polling-path twin of the existing gate on
  Fired actions. This SUPERSEDES the old per-frame OnUpdate early-return, which
  also killed autorun. Gating here instead lets the movement block keep running,
  so autorun — a separate latched bool ORed into Forward at the call site, not a
  polled key — survives. Test updated to encode the new contract.
- GameWindow: the movement suppress-guard reverts to ImGui-devtools-only (the
  retail write mode no longer early-returns); wires DefaultTextInput = the chat
  input (Tab/Enter activation) and Input.Keyboard for clipboard. Drops the
  one-shot UI-scale diagnostic.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.UI.Abstractions/Input/InputDispatcher.cs

@@ -141,6 +141,12 @@ public sealed class InputDispatcher
     public bool IsActionHeld(InputAction action)
     {
         if (action == InputAction.None) return false;
+        // While a text field owns the keyboard ("write mode"), held game actions read as
+        // released: typing "swd" must not move the character. This is the polling-path twin
+        // of the WantCaptureKeyboard gate on Fired actions. NOTE: this suppresses KEY-driven
+        // movement only — latched state that isn't a key (e.g. autorun, ORed into Forward at
+        // the call site) keeps driving the character, so chat doesn't cancel autorun.
+        if (_mouse.WantCaptureKeyboard) return false;
         foreach (var b in _bindings.ForAction(action))
         {
             if (IsChordHeld(b.Chord)) return true;