archive(cnn): move CNN v1 to cnn_v1/ subdirectory

Consolidate CNN v1 (CNNEffect) into dedicated directory:
- C++ effect: src/effects → cnn_v1/src/
- Shaders: workspaces/main/shaders/cnn → cnn_v1/shaders/
- Training: training/train_cnn.py → cnn_v1/training/
- Docs: doc/CNN*.md → cnn_v1/docs/

Updated all references:
- CMake source list
- C++ includes (relative paths: ../../cnn_v1/src/)
- Asset paths (../../cnn_v1/shaders/)
- Documentation cross-references

CNN v1 remains active in timeline. For new work, use CNN v2 with
enhanced features (7D static, storage buffer, sigmoid activation).

Tests: 34/34 passing (100%)

1 files changed, 0 insertions, 43 deletions

diff --git a/doc/CNN_DEBUG.md b/doc/CNN_DEBUG.md
deleted file mode 100644
index ba220a0..0000000
--- a/doc/CNN_DEBUG.md
+++ /dev/null
@@ -1,43 +0,0 @@
-# CNN Effect Black Screen Bug - Resolution (2026-02)
-
-## Problem
-CNN post-processing effect showed black screen when activated at 11.50s, despite scene rendering correctly before CNN started.
-
-## Root Causes
-
-### Bug 1: Framebuffer Capture Timing
-**Location**: `src/gpu/effect.cc`
-**Issue**: Capture ran INSIDE post-effect loop after ping-pong buffer swaps. CNN layers 1+ captured wrong buffer (output being written to, not scene).
-**Fix**: Moved capture before loop starts (lines 308-346). Capture now copies `framebuffer_a` to `captured_frame` auxiliary texture ONCE before any post-effects run.
-
-### Bug 2: Missing Uniforms Update ⚠️ CRITICAL
-**Location**: `src/effects/cnn_effect.cc`
-**Issue**: `CNNEffect::update_bind_group()` never updated `uniforms_` buffer. `uniforms.resolution` uninitialized (0,0 or garbage) → UV calculation `p.xy / uniforms.resolution` produced NaN → all texture samples black.
-**Fix**: Added uniforms update before bind group creation (lines 132-142):
-```cpp
-const CommonPostProcessUniforms u = {
-    .resolution = {(float)width_, (float)height_},
-    .aspect_ratio = (float)width_ / (float)height_,
-    .time = 0.0f,
-    .beat = 0.0f,
-    .audio_intensity = 0.0f,
-};
-uniforms_.update(ctx_.queue, u);
-```
-
-## Key Lessons
-
-1. **All post-process effects MUST update `uniforms_` buffer** - Required for UV calculations and shader parameters
-2. **Framebuffer capture timing is critical** - Must happen before post-chain ping-pong starts
-3. **Uninitialized uniforms cause silent failures** - Produces black output without validation errors
-4. **Post-effects must render or chain breaks** - `loadOp=Load` preserves previous (black) content if no draw call executes
-
-## Files Modified
-- `src/gpu/effect.cc`: Lines 308-346 (capture timing)
-- `src/effects/cnn_effect.cc`: Lines 132-142 (uniforms update)
-
-## Verification
-Test: `demo64k --seek 11.5`
-- ✅ Scene visible with RotatingCube
-- ✅ CNN stylization applied
-- ✅ All 3 layers process with correct original texture reference