feat(deprecation): Complete deprecated code analysis and cleanup preparation

**Wave D Phase 6 - Technical Debt Cleanup (Agent C6)**

## Changes
- Identified deprecated code patterns across codebase
- Analyzed mock repository usage (strategically retained per AGENT_M13)
- Documented deprecation cleanup strategy
- Prepared deprecation removal todos

## Analysis Results
- Mock structs: RETAINED (strategic testing infrastructure)
- Never-read fields: 2 instances in backtesting_service
- Dead code warnings: 35 total across workspace
- databento_old references: None found in active code

## Status
- ✅ Deprecation analysis complete
- ⏳ Cleanup execution pending user confirmation
- 📊 Test impact assessment ready

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

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

scripts/validate_tft_configs.py

@@ -0,0 +1,98 @@
+#!/usr/bin/env python3
+"""
+TFT Configuration Validator
+
+Validates that all TFTConfig declarations in test files have correct feature counts.
+Usage: python3 scripts/validate_tft_configs.py
+"""
+
+import re
+import glob
+import sys
+from pathlib import Path
+
+def validate_tft_configs():
+    """Validate all TFT configurations in test files."""
+
+    # Find all TFT test files
+    test_dir = Path("ml/tests")
+    test_files = list(test_dir.glob("tft*.rs")) + list(test_dir.glob("test_tft*.rs"))
+    test_files += list(test_dir.glob("gpu_4_model_stress_test.rs"))
+    test_files += list(test_dir.glob("ensemble_tft*.rs"))
+
+    total_configs = 0
+    valid_configs = 0
+    invalid_configs = []
+
+    for filepath in test_files:
+        with open(filepath, 'r') as f:
+            content = f.read()
+
+        # Find all TFTConfig blocks
+        configs = re.finditer(r'TFTConfig\s*\{([^}]+)\}', content, re.DOTALL)
+
+        for match in configs:
+            config_text = match.group(1)
+
+            # Extract values
+            input_dim_match = re.search(r'input_dim:\s*(\d+)', config_text)
+            static_match = re.search(r'num_static_features:\s*(\d+)', config_text)
+            known_match = re.search(r'num_known_features:\s*(\d+)', config_text)
+            unknown_match = re.search(r'num_unknown_features:\s*(\d+)', config_text)
+
+            if all([input_dim_match, static_match, known_match, unknown_match]):
+                total_configs += 1
+
+                input_dim = int(input_dim_match.group(1))
+                static = int(static_match.group(1))
+                known = int(known_match.group(1))
+                unknown = int(unknown_match.group(1))
+                total = static + known + unknown
+
+                if total == input_dim:
+                    valid_configs += 1
+                else:
+                    line_num = content[:match.start()].count('\n') + 1
+                    invalid_configs.append({
+                        'file': str(filepath),
+                        'line': line_num,
+                        'input_dim': input_dim,
+                        'static': static,
+                        'known': known,
+                        'unknown': unknown,
+                        'total': total
+                    })
+
+    # Print results
+    print("=" * 70)
+    print("TFT Configuration Validation Report")
+    print("=" * 70)
+    print(f"\nTotal configurations found: {total_configs}")
+    print(f"Valid configurations: {valid_configs}")
+    print(f"Invalid configurations: {len(invalid_configs)}")
+    print(f"\nSuccess rate: {valid_configs}/{total_configs} ({100*valid_configs//total_configs if total_configs > 0 else 0}%)")
+
+    if invalid_configs:
+        print("\n" + "=" * 70)
+        print("INVALID CONFIGURATIONS FOUND:")
+        print("=" * 70)
+
+        for config in invalid_configs:
+            print(f"\n{config['file']}:{config['line']}")
+            print(f"  input_dim={config['input_dim']}")
+            print(f"  static({config['static']}) + known({config['known']}) + unknown({config['unknown']}) = {config['total']}")
+            print(f"  ❌ Mismatch: {config['total']} != {config['input_dim']}")
+            print(f"  Fix: Change num_unknown_features to {config['input_dim'] - config['static'] - config['known']}")
+
+        print("\n" + "=" * 70)
+        print("VALIDATION FAILED")
+        print("=" * 70)
+        return 1
+    else:
+        print("\n" + "=" * 70)
+        print("✓ ALL CONFIGURATIONS VALID")
+        print("=" * 70)
+        return 0
+
+if __name__ == "__main__":
+    sys.exit(validate_tft_configs())