fix: fxcache key match with MBP-10 + trades data paths

- Add mbp10_data_dir and trades_data_dir to smoketest TOML profile
- Fix data_loading path resolution: resolve relative paths against
  workspace root via CARGO_MANIFEST_DIR (CWD is crates/ml during tests)
- Add buffer_size floor of 1024 in hyperopt adapter (GPU PER minimum)
- Regenerated fxcache with full OFI features (MBP-10 + trades)

All tests now consistently hit fxcache with OFI=true.

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

config/training/dqn-smoketest.toml

@@ -22,6 +22,9 @@ reward_scale = 1.0
 huber_delta = 1.0
 symbol = "ES.FUT"
 max_bars = 5000
+data_source = "ohlcv"
+mbp10_data_dir = "test_data/futures-baseline-mbp10"
+trades_data_dir = "test_data/futures-baseline-trades"
 imbalance_bar_threshold = 1.0
 imbalance_bar_ewma_alpha = 0.1
 

crates/ml/src/trainers/dqn/data_loading.rs

@@ -100,18 +100,29 @@ impl DQNTrainer {
     )> {
         // ── fxcache discovery (strict key match via shared function) ────────
         let cache_dir_override = self.feature_cache_dir.as_deref();
-        let mbp10_path = if self.hyperparams.mbp10_data_dir.is_empty() {
+        // Resolve mbp10/trades paths — try as-is first, then relative to workspace root
+        // (CARGO_MANIFEST_DIR points to crates/ml, workspace root is 2 levels up).
+        let resolve_data_path = |raw: &str| -> Option<std::path::PathBuf> {
+            if raw.is_empty() { return None; }
+            let p = std::path::Path::new(raw);
+            if p.exists() { return Some(p.to_path_buf()); }
+            // Try relative to workspace root
+            if let Ok(manifest) = std::env::var("CARGO_MANIFEST_DIR") {
+                if let Some(root) = std::path::Path::new(&manifest).parent().and_then(|p| p.parent()) {
+                    let abs = root.join(raw);
+                    if abs.exists() { return Some(abs); }
+                }
+            }
+            // Try relative to dbn_data_dir's parent (e.g. test_data/futures-baseline → test_data/)
+            let parent = std::path::Path::new(dbn_data_dir).parent().unwrap_or(std::path::Path::new("."));
+            let sibling = parent.join(std::path::Path::new(raw).file_name().unwrap_or_default());
+            if sibling.exists() { return Some(sibling); }
             None
-        } else {
-            let p = std::path::Path::new(&self.hyperparams.mbp10_data_dir);
-            if p.exists() { Some(p) } else { None }
-        };
-        let trades_path = if self.hyperparams.trades_data_dir.is_empty() {
-            None
-        } else {
-            let p = std::path::Path::new(&self.hyperparams.trades_data_dir);
-            if p.exists() { Some(p) } else { None }
         };
+        let mbp10_resolved = resolve_data_path(&self.hyperparams.mbp10_data_dir);
+        let trades_resolved = resolve_data_path(&self.hyperparams.trades_data_dir);
+        let mbp10_path = mbp10_resolved.as_deref();
+        let trades_path = trades_resolved.as_deref();
 
         if let Some(cached) = crate::fxcache::discover_and_load(
             std::path::Path::new(dbn_data_dir),