docs: Fix EFFECT keyword syntax and add automation-friendly workflow

Fix EFFECT keyword format across all documentation and scripts - priority
modifier (+/=/–) is required but was missing from examples.

**Documentation fixes:**
- doc/HOWTO.md: Added missing + to EFFECT example
- doc/RECIPE.md: Added priority modifiers to examples
- tools/shadertoy/README.md: Fixed test path, clarified workflow
- tools/shadertoy/convert_shadertoy.py: Updated output instructions

**New automation guide:**
- doc/EFFECT_WORKFLOW.md: Complete step-by-step checklist for AI agents
  - Exact file paths and line numbers
  - Common issues and fixes
  - Asset ID naming conventions
  - CMakeLists.txt dual-section requirement
  - Test list instructions (post_process_effects vs scene_effects)

**Integration:**
- CLAUDE.md: Added EFFECT_WORKFLOW.md to Tier 2 (always loaded)
- doc/AI_RULES.md: Added "Adding Visual Effects" quick reference
- README.md: Added EFFECT_WORKFLOW.md to documentation list

**CMakeLists.txt:**
- Disabled incomplete cube_sphere_effect.cc (ShaderToy conversion WIP)

**Timeline:**
- Commented out incomplete CubeSphereEffect
- Removed obsolete constructor argument

Fixes #issue-with-effect-syntax

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 9 insertions, 6 deletions

diff --git a/doc/CONTRIBUTING.md b/doc/CONTRIBUTING.md
index 9cd785b..98df873 100644
--- a/doc/CONTRIBUTING.md
+++ b/doc/CONTRIBUTING.md
@@ -65,12 +65,15 @@ See `doc/CODING_STYLE.md` for detailed examples.
 ## Development Protocols
 
 ### Adding Visual Effect
-1. Implement `Effect` subclass in `src/gpu/demo_effects.cc`
-2. Add to workspace `timeline.seq` (e.g., `workspaces/main/timeline.seq`)
-3. **Update `test_demo_effects.cc`**:
-   - Add to test list
-   - Increment `EXPECTED_*_COUNT`
-4. Verify:
+1. Create effect class files (use `tools/shadertoy/convert_shadertoy.py` or templates)
+2. Add shader to `workspaces/main/assets.txt`
+3. Add effect `.cc` file to `CMakeLists.txt` GPU_SOURCES (both sections)
+4. Include header in `src/gpu/demo_effects.h`
+5. Add to workspace `timeline.seq` (e.g., `workspaces/main/timeline.seq`)
+6. **Update `src/tests/gpu/test_demo_effects.cc`**:
+   - Add to `post_process_effects` list (lines 80-93) or `scene_effects` list (lines 125-137)
+   - Example: `{"MyEffect", std::make_shared<MyEffect>(fixture.ctx())},`
+7. Verify:
 ```bash
 cmake -S . -B build -DDEMO_BUILD_TESTS=ON
 cmake --build build -j4 --target test_demo_effects