docs: Update Task A status - artifacts fixed but shadows missing

Task A progress:
✅ Mesh normal transformation fixed (shader double-transpose bug)
✅ Quaternion rotation stretching fixed (axis normalization)
✅ Mesh shadow scaling fixed (excluded from SDF scale factor)
✅ Floor rendering artifacts fixed (PLANE → BOX workaround)

Remaining issues:
- Task A.1: Missing shadows in test_mesh (needs investigation)
- Task A.2: ObjectType::PLANE broken with non-uniform scaling
  - Root cause: sdPlane doesn't handle non-uniform scale in local space
  - Workaround applied: Using BOX instead of PLANE for floor
  - Need to determine if PLANE should support this or is unsupported by design

handoff(Claude): Test mesh visual artifacts resolved, but PLANE object type
has fundamental issues with non-uniform scaling. Workaround in place, but
proper fix requires deeper investigation into SDF distance field math.

1 files changed, 11 insertions, 4 deletions

diff --git a/TODO.md b/TODO.md
index da556b8..19edaf6 100644
--- a/TODO.md
+++ b/TODO.md
@@ -139,10 +139,17 @@ This file tracks prioritized tasks with detailed attack plans.
 
 ## Critical Fixes
 
-- [ ] **Task A: Fix Test Mesh**
-    - [ ] Investigate and fix bad bounding box (clipping at the bottom) for `dodecahedron.obj`.
-    - [ ] Investigate and fix strange normals for `dodecahedron.obj`.
-    - [ ] Fix incorrect shadows on the floor plane.
+- [ ] **Task A: Fix Test Mesh** (Partially Complete)
+    - [x] Fixed mesh normal transformation bug (double-transpose in shaders)
+    - [x] Fixed quaternion rotation stretching (non-normalized axis in quat::from_axis)
+    - [x] Fixed mesh shadow scaling (excluded meshes from SDF scale factor)
+    - [x] Fixed floor rendering artifacts (changed from PLANE to BOX)
+    - [ ] **Task A.1**: Investigate and fix missing shadows in test_mesh
+    - [ ] **Task A.2**: Investigate and fix ObjectType::PLANE with non-uniform scaling
+      - **Issue**: PLANE with extreme non-uniform scaling (e.g., vec3(20, 0.01, 20)) causes incorrect SDF distance calculations in shadows
+      - **Workaround**: Changed test_mesh floor to use ObjectType::BOX instead
+      - **Root Cause**: sdPlane distance calculation doesn't account for non-uniform scaling when transformed to local space
+      - **Investigation needed**: Determine if PLANE should handle non-uniform scaling or if it's unsupported by design
 
 - [ ] **Task B: Move platform-specific conditional code into a single header location**
     - [ ] Abstract out `#if defined(DEMO_CROSS_COMPILE_WIN32)` statements from core `.cc` and `.h` sources.