fix(ui): Phase K live-test fixes pt4 — collision wires default OFF, refresh DebugPanel cheat-sheet

User reported "I can't turn off collision wires" — root cause was
two-fold: the wires defaulted to ON at startup so the user saw
them every launch, and the DebugPanel's keybind cheat-sheet
still listed the pre-K.1c retail-default-conflicting bindings
(F1/F2/F3/F7/F8/F9/F10 etc.) instead of the Ctrl+F* aliases the
retail-faithful keymap moved them to.

Changes:

- _debugCollisionVisible defaults to FALSE. Ctrl+F2 toggles it
  on (toast: "Collision wireframes ON"); the DebugPanel →
  Diagnostics → "Toggle collision wires" button toggles too.

- DebugPanel "Help" cheat-sheet rebuilt to reflect the actual
  retail-default + Phase K bindings: Ctrl+F1 (debug), Ctrl+F2
  (collision wires), Ctrl+Shift+F (free-fly), F11 (Settings),
  W/X = forward/back, A/D = turn, Z/C = strafe, Q = autorun
  toggle, Shift = walk modifier, Y/G/H/B = postures,
  Hold MMB = instant mouse-look, Hold RMB = orbit, Tab =
  focus chat input. The user no longer has to read the source
  to find a working binding.

Tests stay 1222 green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -27,7 +27,11 @@ public sealed class GameWindow : IDisposable
     private Shader? _meshShader;
     private TextureCache? _textureCache;
     private DebugLineRenderer? _debugLines;
-    private bool _debugCollisionVisible = true;
+    // K-fix4 (2026-04-26): default OFF. The orange BSP / green cylinder
+    // wireframes are noisy outdoors and confuse first-time users into
+    // thinking they're a rendering bug. Ctrl+F2 toggles, the DebugPanel
+    // → Diagnostics → "Toggle collision wires" button toggles too.
+    private bool _debugCollisionVisible = false;
     private int _debugDrawLogOnce = 0;
 
     // Phase I.2: the old StbTrueTypeSharp DebugOverlay was deleted in