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.Core/Physics/ShadowObjectRegistry.cs

@@ -23,10 +23,13 @@ public sealed class ShadowObjectRegistry
     public void Register(uint entityId, uint gfxObjId, Vector3 worldPos, Quaternion rotation,
                          float radius, float worldOffsetX, float worldOffsetY, uint landblockId,
                          ShadowCollisionType collisionType = ShadowCollisionType.BSP,
-                         float cylHeight = 0f)
+                         float cylHeight = 0f, float scale = 1.0f)
     {
         Deregister(entityId);
 
+        // The radius parameter should already be the WORLD-SPACE bounding
+        // radius (i.e., already multiplied by scale) so the broad-phase cell
+        // occupancy is correct. Callers are responsible for that.
         float localX = worldPos.X - worldOffsetX;
         float localY = worldPos.Y - worldOffsetY;
 
@@ -35,7 +38,7 @@ public sealed class ShadowObjectRegistry
         int minCy = Math.Max(0, (int)((localY - radius) / 24f));
         int maxCy = Math.Min(7, (int)((localY + radius) / 24f));
 
-        var entry = new ShadowEntry(entityId, gfxObjId, worldPos, rotation, radius, collisionType, cylHeight);
+        var entry = new ShadowEntry(entityId, gfxObjId, worldPos, rotation, radius, collisionType, cylHeight, scale);
         var cellIds = new List<uint>();
 
         uint lbPrefix = landblockId & 0xFFFF0000u;
@@ -166,6 +169,24 @@ public sealed class ShadowObjectRegistry
     }
 
     public int TotalRegistered => _entityToCells.Count;
+
+    /// <summary>
+    /// Debug: enumerate every registered ShadowEntry (deduplicated across cells).
+    /// For each entity, returns the first entry found in any cell it occupies.
+    /// Intended for debug rendering only.
+    /// </summary>
+    public IEnumerable<ShadowEntry> AllEntriesForDebug()
+    {
+        var seen = new HashSet<uint>();
+        foreach (var kvp in _cells)
+        {
+            foreach (var entry in kvp.Value)
+            {
+                if (seen.Add(entry.EntityId))
+                    yield return entry;
+            }
+        }
+    }
 }
 
 /// <summary>
@@ -181,4 +202,5 @@ public readonly record struct ShadowEntry(
     Quaternion Rotation,
     float Radius,
     ShadowCollisionType CollisionType = ShadowCollisionType.BSP,
-    float CylHeight = 0f);
+    float CylHeight = 0f,
+    float Scale = 1.0f);