docs(TODO): add test infrastructure maintenance section

Documented outstanding test TODOs:
- test_effect_base.cc:250 - SIGTRAP in test_sequence_render (commented out)
- test_sequence.cc - v1 to v2 port pending
- test_audio_engine.cc:152 - Commented test needs debugging
- test_fft.cc:87 - FFT-DCT algorithm investigation

All tests currently passing (35/35)

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

1 files changed, 21 insertions, 0 deletions

diff --git a/TODO.md b/TODO.md
index e7aec46..e78ce0a 100644
--- a/TODO.md
+++ b/TODO.md
@@ -46,6 +46,27 @@ Enhanced CNN post-processing with multi-dimensional feature inputs.
 
 ---
 
+## Priority 3: Test Infrastructure Maintenance [ONGOING]
+
+**Status:** 35/35 tests passing
+
+**Outstanding TODOs:**
+
+1. **test_effect_base.cc:250** - Fix SIGTRAP in `test_sequence_render()` (commented out)
+   - All other tests validate the same functionality
+   - Issue: Hangs/crashes during render with external sink view
+
+2. **test_sequence.cc** - Port v1 sequence tests to v2 (currently disabled)
+   - Uses legacy Effect/MainSequence system
+   - Lines 168, 173, 182: Re-enable lifecycle and simulation tests after v2 port
+
+3. **test_audio_engine.cc:152** - Re-enable commented test after debugging
+
+4. **test_fft.cc:87** - Investigate FFT-DCT algorithm discrepancy
+   - May need different algorithm or fix existing one
+
+---
+
 ## ~~Priority 3: Tracker Humanization & Sample Offset~~ [IMPLEMENTED]
 
 Enhance tracker with sample offset and humanization for realistic playback.