fix: point data_dir to features/ subdir where .npz and audio live

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

experiments/tier1_sweep.json

@@ -1,7 +1,7 @@
 {
   "name": "tier1_sweep",
   "description": "Ablation of Tier 1 improvements: LoRA+, dropout, curriculum sampling. Baseline = uniform, no regularisation.",
-  "data_dir": "/media/unraid/davinci/Selva/BJ",
+  "data_dir": "/media/unraid/davinci/Selva/BJ/features",
   "output_root": "lora_sweeps/tier1_sweep",
   "base": {
     "steps": 4000,

experiments/tier1_thorough.json

@@ -1,7 +1,7 @@
 {
   "name": "tier1_thorough",
   "description": "Full overnight Tier 1 ablation on 49-clip BJ dataset. 4 groups: rank, alpha, regularisation, and best combinations. ~10-12h depending on GPU.",
-  "data_dir": "/media/unraid/davinci/Selva/BJ",
+  "data_dir": "/media/unraid/davinci/Selva/BJ/features",
   "output_root": "/media/unraid/davinci/Selva/BJ/experiment/tier1_thorough",
   "base": {
     "steps": 4000,