feat(ml): WAVE 29 DQN Codebase Cleanup & Refactoring Campaign

BREAKING CHANGES:
- Removed orphaned dqn.rs monolithic trainer (4,975 lines)
- Removed orphaned dqn_ensemble.rs module (816 lines)
- Removed orphaned tft.rs and tft_complete_int8_integration_test.rs
- TFT trainer split into modular directory structure

DQN Module Refactoring:
- Split trainers/dqn.rs into modular structure (config.rs, statistics.rs, trainer.rs)
- Fixed hyperopt 39D search space (continuous params only)
- Boolean flags (use_dueling, use_double_dqn, use_per, use_noisy_nets) are now FIXED architectural decisions
- use_distributional defaults to false (Candle BUG #36 - scatter_add gradient issues)

Clean Module Structure:
- ml/src/trainers/dqn/ directory with proper mod.rs exports
- ml/src/trainers/tft/ directory with config.rs, types.rs, model.rs, trainer.rs, tests.rs
- All P0 features validated: TD-error clamping, batch diversity, LR scheduler, priority staleness

Documentation:
- Added comprehensive docs in docs/codebase-cleanup/
- ADR-001 for DQN refactoring decisions
- Rainbow DQN component matrix and quick reference guides

Build Status: Compiles with zero errors

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docs/codebase-cleanup/wave28_3_report.txt

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+# WAVE 28.3: Import Update Summary
+
+## Task Completed
+Updated all imports from `WorkingDQN`/`WorkingDQNConfig` to `DQN`/`DQNConfig` and removed deprecated `config_2025` and `demo_2025_dqn` modules.
+
+## Files Changed
+
+### Core DQN Files
+1. `/home/jgrusewski/Work/foxhunt/ml/src/lib_test.rs`
+   - Changed: `WorkingDQN` → `DQN`
+   - Changed: `WorkingDQNConfig` → `DQNConfig`
+
+2. `/home/jgrusewski/Work/foxhunt/ml/src/dqn/mod.rs`
+   - Removed: `pub mod demo_2025_dqn;`
+   - Removed: `pub mod config_2025;`
+   - Removed: Re-exports of `config_2025` functions
+   - Updated: `pub use dqn::{DQN, DQNConfig}`
+   - Removed: Duplicate `DQNConfig` from agent module export
+
+3. `/home/jgrusewski/Work/foxhunt/ml/src/dqn/regime_conditional.rs`
+   - Changed: `WorkingDQN` → `DQN` (7 occurrences)
+   - Changed: `WorkingDQNConfig` → `DQNConfig` (4 occurrences)
+   - Updated documentation examples
+
+4. `/home/jgrusewski/Work/foxhunt/ml/src/dqn/ensemble.rs`
+   - Changed: `WorkingDQN` → `DQN` (5 occurrences)
+   - Changed: `WorkingDQNConfig` → `DQNConfig` (4 occurrences)
+   - Updated documentation examples
+
+5. `/home/jgrusewski/Work/foxhunt/ml/src/dqn/distributional_dueling.rs`
+   - Changed: Comment from `WorkingDQNConfig` → `DQNConfig`
+
+6. `/home/jgrusewski/Work/foxhunt/ml/src/dqn/dueling.rs`
+   - Changed: Comment from `WorkingDQNConfig` → `DQNConfig`
+
+### Adapter & Benchmark Files
+7. `/home/jgrusewski/Work/foxhunt/ml/src/dqn/trainable_adapter.rs`
+   - Changed: `WorkingDQN` → `DQN` (6 occurrences)
+   - Changed: `WorkingDQNConfig` → `DQNConfig` (6 occurrences)
+   - Updated all documentation references
+
+8. `/home/jgrusewski/Work/foxhunt/ml/src/benchmark/dqn_benchmark.rs`
+   - Changed: `WorkingDQN` → `DQN` (4 occurrences)
+   - Changed: `WorkingDQNConfig` → `DQNConfig` (2 occurrences)
+   - Updated model_name from "WorkingDQN" to "DQN"
+
+### Trainer Files
+9. `/home/jgrusewski/Work/foxhunt/ml/src/trainers/dqn/config.rs`
+   - Changed: `WorkingDQN` → `DQN` (3 occurrences)
+   - Updated comments referencing `WorkingDQNConfig`
+
+10. `/home/jgrusewski/Work/foxhunt/ml/src/trainers/dqn/trainer.rs`
+    - Changed: `WorkingDQN` → `DQN` (2 occurrences)
+    - Changed: `WorkingDQNConfig` → `DQNConfig` (2 occurrences)
+
+11. `/home/jgrusewski/Work/foxhunt/ml/src/trainers/dqn_ensemble.rs`
+    - Changed: `WorkingDQN` → `DQN` (3 occurrences)
+    - Changed: `WorkingDQNConfig` → `DQNConfig` (1 occurrence)
+
+### Hyperopt Files
+12. `/home/jgrusewski/Work/foxhunt/ml/src/hyperopt/adapters/dqn.rs`
+    - Changed: All references automatically via sed
+
+## Changes Summary
+
+### Replacements Made
+- **WorkingDQN** → **DQN**: 35+ occurrences
+- **WorkingDQNConfig** → **DQNConfig**: 30+ occurrences
+
+### Modules Deprecated
+- `ml/src/dqn/config_2025.rs` - Commented out in mod.rs
+- `ml/src/dqn/demo_2025_dqn.rs` - Commented out in mod.rs
+
+### Build Status
+✅ **SUCCESS**: `cargo check --package ml` completes without errors
+- Only warnings (unused imports, deprecated types in other modules)
+- No compilation errors
+- All refactored code compiles cleanly
+
+## Next Steps
+The codebase now consistently uses:
+- `DQN` instead of `WorkingDQN`
+- `DQNConfig` instead of `WorkingDQNConfig`
+- Main dqn module instead of deprecated config_2025 module
+
+All imports have been updated and the code compiles successfully.