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>

archive/scripts/test_dqn_initialization.sh

@@ -0,0 +1,65 @@
+#!/bin/bash
+# Test script to verify DQN initialization is non-deterministic
+# Runs 3 parallel training instances and extracts initial Q-values
+
+set -e
+
+echo "=== DQN Non-Deterministic Initialization Test ==="
+echo "Starting 3 parallel training runs with 1 epoch each..."
+echo ""
+
+# Clean up old test outputs
+rm -rf /tmp/init_test_* 2>/dev/null || true
+
+# Run 3 training instances in parallel
+cargo run --package ml --example train_dqn --release --features cuda -- \
+  --epochs 1 --output-dir /tmp/init_test_1 > /tmp/init_test_1.log 2>&1 &
+PID1=$!
+
+cargo run --package ml --example train_dqn --release --features cuda -- \
+  --epochs 1 --output-dir /tmp/init_test_2 > /tmp/init_test_2.log 2>&1 &
+PID2=$!
+
+cargo run --package ml --example train_dqn --release --features cuda -- \
+  --epochs 1 --output-dir /tmp/init_test_3 > /tmp/init_test_3.log 2>&1 &
+PID3=$!
+
+echo "Waiting for training runs to complete..."
+echo "  PID $PID1 (test 1)"
+echo "  PID $PID2 (test 2)"
+echo "  PID $PID3 (test 3)"
+echo ""
+
+wait $PID1 $PID2 $PID3
+
+echo "All training runs completed. Extracting Q-values..."
+echo ""
+
+# Extract initial Q-values from logs
+echo "=== Run 1 - Initial Q-Values ==="
+grep -E "Step 0.*Q-values:" /tmp/init_test_1.log | head -1 || echo "No Q-values found in Run 1"
+echo ""
+
+echo "=== Run 2 - Initial Q-Values ==="
+grep -E "Step 0.*Q-values:" /tmp/init_test_2.log | head -1 || echo "No Q-values found in Run 2"
+echo ""
+
+echo "=== Run 3 - Initial Q-Values ==="
+grep -E "Step 0.*Q-values:" /tmp/init_test_3.log | head -1 || echo "No Q-values found in Run 3"
+echo ""
+
+# Extract entropy seeds
+echo "=== Entropy Seeds Used ==="
+echo "Run 1:"
+grep "Device RNG seeded with entropy:" /tmp/init_test_1.log | head -1 || echo "No seed found"
+echo "Run 2:"
+grep "Device RNG seeded with entropy:" /tmp/init_test_2.log | head -1 || echo "No seed found"
+echo "Run 3:"
+grep "Device RNG seeded with entropy:" /tmp/init_test_3.log | head -1 || echo "No seed found"
+echo ""
+
+echo "=== Validation ==="
+echo "SUCCESS: If the Q-values and seeds are DIFFERENT across runs, the fix is working!"
+echo "FAILURE: If the Q-values are IDENTICAL across runs, the issue persists."
+echo ""
+echo "Logs saved to: /tmp/init_test_{1,2,3}.log"