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>

scripts/analyze_dead_code.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+# Dead Code Analysis Script for Foxhunt Workspace
+
+echo "=== FOXHUNT DEAD CODE ANALYSIS ==="
+echo ""
+
+# 1. Find public items that might be unused
+echo "1. PUBLIC API SURFACE ANALYSIS"
+echo "-------------------------------"
+find . -name "*.rs" -type f -not -path "./target/*" -exec grep -l "^pub fn\|^pub struct\|^pub enum\|^pub trait" {} \; | wc -l
+echo " files with public items found"
+echo ""
+
+# 2. Find large commented code blocks
+echo "2. LARGE COMMENTED CODE BLOCKS (>10 lines)"
+echo "-------------------------------------------"
+find . -name "*.rs" -type f -not -path "./target/*" -print0 | while IFS= read -r -d '' file; do
+    awk '/^[[:space:]]*\/\// {count++} !/^[[:space:]]*\/\// {if (count >= 10) print FILENAME":"NR-count"-"NR-1":"count" lines"; count=0} END {if (count >= 10) print FILENAME":"NR-count"-"NR":"count" lines"}' "$file"
+done | head -20
+echo ""
+
+# 3. Find empty or nearly empty modules
+echo "3. EMPTY OR MINIMAL MODULES"
+echo "----------------------------"
+find . -name "*.rs" -type f -not -path "./target/*" -exec sh -c 'lines=$(wc -l < "$1"); if [ "$lines" -lt 10 ]; then echo "$1: $lines lines"; fi' _ {} \; | head -20
+echo ""
+
+# 4. Find test modules with no tests
+echo "4. TEST MODULES WITHOUT TESTS"
+echo "------------------------------"
+find . -name "*.rs" -type f -not -path "./target/*" -exec grep -l "#\[cfg(test)\]" {} \; | while read file; do
+    if ! grep -q "#\[test\]" "$file"; then
+        echo "$file - has #[cfg(test)] but no #[test] functions"
+    fi
+done | head -10
+echo ""
+
+# 5. Find feature-gated code
+echo "5. FEATURE-GATED CODE"
+echo "----------------------"
+find . -name "*.rs" -type f -not -path "./target/*" -exec grep -l "#\[cfg(feature" {} \; | head -10
+echo ""
+
+# 6. Analyze Cargo.toml dependencies
+echo "6. DEPENDENCY ANALYSIS PER CRATE"
+echo "---------------------------------"
+find . -name "Cargo.toml" -not -path "./target/*" | head -5
+echo ""
+
+echo "=== ANALYSIS COMPLETE ==="