feat(ui): debug overlay + refined input controls

Adds the first on-screen HUD for the dev client plus today's mouse-control
refinements. Also lands yesterday's scenery-alignment changes that were
left uncommitted in the working tree.

Overlay:
- BitmapFont rasterizes a system TTF via StbTrueTypeSharp into a 512x512
  R8 atlas at startup (Consolas on Windows, DejaVu/Menlo fallbacks)
- TextRenderer batches 2D quads in screen-space with ortho projection;
  one shader + two draw calls (rect then text) for panel backgrounds
  under glyphs
- DebugOverlay composes info / stats / compass / help panels on top of
  the 3D scene; toggles via F1/F4/F5/F6; transient toasts for key events
- DebugLineRenderer and its shaders (carried over from the scenery work)
  are properly committed in this commit

Controls:
- Per-mode mouse sensitivity (Chase 0.15, Fly 1.0, Orbit 1.0); F8/F9 to
  adjust the active mode multiplicatively (x1.2)
- Hold RMB to free-orbit the chase camera around the player; release
  stays at the new angle (no snap-back)
- Mouse-wheel zooms chase distance between 2m and 40m
- Chase pitch widened to [-0.7, 1.4] so mouse-Y tilts both ways from
  the default neutral angle

Scenery alignment (carried from yesterday's session):
- ShadowObjectRegistry AllEntriesForDebug + Scale field
- SceneryGenerator uses ACViewer's OnRoad polygon test + baseLoc +
  set_heading rotation
- BSPQuery dispatchers accept localToWorld so normals/offsets transform
  correctly per part
- TransitionTypes.CylinderCollision rewritten with wall-slide + push-out
- PhysicsDataCache caches visual-mesh AABB for scenery that lacks
  physics Setup bounds

src/AcDream.App/AcDream.App.csproj

@@ -15,6 +15,7 @@
     <PackageReference Include="Silk.NET.Input" Version="2.23.0" />
     <PackageReference Include="Serilog" Version="4.0.2" />
     <PackageReference Include="Serilog.Sinks.Console" Version="6.0.0" />
+    <PackageReference Include="StbTrueTypeSharp" Version="1.26.12" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\AcDream.Core\AcDream.Core.csproj" />