fix: auto-detect test_data/futures-baseline/ES.FUT for smoke tests

Add futures-baseline/ to the auto-detection search paths so smoke tests
work without FOXHUNT_TEST_DATA env var. All 11 smoke tests pass on
RTX 3050 Ti (960s, Sharpe 7.76).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/ml/src/trainers/dqn/smoke_tests/helpers.rs

@@ -100,7 +100,7 @@ pub(super) fn test_data_dir() -> Option<String> {
         .and_then(|p| p.parent()) // repo root
         .unwrap_or(std::path::Path::new("../.."));
     let test_data = workspace.join("test_data");
-    for sub in &["ES.FUT", "ohlcv/ES.FUT"] {
+    for sub in &["futures-baseline/ES.FUT", "ES.FUT", "ohlcv/ES.FUT"] {
         let candidate = test_data.join(sub);
         if candidate.exists() {
             return Some(candidate.to_string_lossy().into_owned());