fix(ml): Fix 3 pre-existing test failures (Part 2/3)

Fixed Tests:
1. test_output_shape_validation - Added transpose for cached weights in quantized attention
2. test_weight_caching - Same fix as #1, ensures consistency between cached and non-cached paths
3. test_training_step_with_data - Fixed DQN dtype mismatch by converting next_state_values to F32

Root Causes:
- Quantized attention: Cached weights were not transposed like slow path weights
- DQN: next_q_values.max(1) returns F64, causing dtype mismatch with F32 tensors

Files Modified:
- ml/src/tft/quantized_attention.rs: Added .t()? for cached weight projections (lines 238-240, 296)
- ml/src/dqn/dqn.rs: Added .to_dtype(DType::F32)? for next_state_values (lines 477, 483)

Test Results: 1286/1290 passing (4 failures remaining, down from 8)

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

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

data/tests/parquet_persistence_tests.rs

@@ -454,6 +454,9 @@ async fn test_trade_events() {
         quantity: Some(0.1),
         sequence: 1,
         latency_ns: Some(1000),
+        open: None,
+        high: None,
+        low: None,
     };
 
     writer.record(event).unwrap();
@@ -517,6 +520,9 @@ async fn test_orderbook_events() {
         quantity: None,
         sequence: 1,
         latency_ns: Some(2000),
+        open: None,
+        high: None,
+        low: None,
     };
 
     writer.record(event).unwrap();
@@ -558,6 +564,9 @@ async fn test_mixed_event_types() {
             quantity: None,
             sequence: 3,
             latency_ns: None,
+            open: None,
+            high: None,
+            low: None,
         },
     ];
 
@@ -883,6 +892,9 @@ async fn test_extreme_values() {
         quantity: Some(f64::MIN_POSITIVE),
         sequence: u64::MAX,
         latency_ns: Some(u64::MAX),
+        open: None,
+        high: None,
+        low: None,
     };
 
     let result = writer.record(event);
@@ -921,6 +933,9 @@ async fn test_null_optional_fields() {
         quantity: None,
         sequence: 1,
         latency_ns: None,
+        open: None,
+        high: None,
+        low: None,
     };
 
     let result = writer.record(event);
@@ -1214,6 +1229,9 @@ async fn test_negative_timestamp_handling() {
         quantity: Some(1.0),
         sequence: 1,
         latency_ns: Some(1000),
+        open: None,
+        high: None,
+        low: None,
     };
 
     let result = writer.record(event);
@@ -1239,6 +1257,9 @@ async fn test_nan_and_infinity_values() {
         quantity: Some(f64::NAN),
         sequence: 1,
         latency_ns: Some(1000),
+        open: None,
+        high: None,
+        low: None,
     };
 
     let result = writer.record(event_nan);
@@ -1256,6 +1277,9 @@ async fn test_nan_and_infinity_values() {
         quantity: Some(f64::NEG_INFINITY),
         sequence: 2,
         latency_ns: Some(2000),
+        open: None,
+        high: None,
+        low: None,
     };
 
     let result = writer.record(event_inf);