feat(data): expand platinum to 176 drugs via OpenFDA extraction

OpenFDA API mining: 5,000 labels → 177 extractions → 29 new validated drugs
Quality filters: dose ≥ 1mg, Cmax/dose ∈ [1e-6, 0.5], SMILES available

Holdout expanded: 71 → 100 drugs (29 truly unseen OpenFDA drugs)
Removed 7 bad extractions (dose=0, impossible Cmax/dose, known prodrugs)

Honest performance on expanded holdout:
  Tier 1 ALL (99 drugs): AAFE 2.903 [2.34, 3.67]
  Tier 2 Mechanistic AD (90 drugs): AAFE 2.563 [2.11, 3.18]

The expanded set gives MORE HONEST generalization estimate:
  - Previous Tier 2 (62 drugs): AAFE 2.329 (curated, selection bias)
  - Expanded Tier 2 (90 drugs): AAFE 2.563 (includes automated extraction)
  - Delta +0.234 reflects genuinely harder unseen drugs

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

Author: jam-sudo

data/clinical/holdout_split.json

@@ -148,11 +148,40 @@
     "vilazodone",
     "vonoprazan",
     "zolpidem",
-    "zonisamide"
+    "zonisamide",
+    "indomethacin",
+    "ranolazine",
+    "sildenafil",
+    "pravastatin",
+    "penicillamine",
+    "carbinoxamine",
+    "atovaquone",
+    "febuxostat",
+    "levofloxacin",
+    "sumatriptan",
+    "fluvoxamine",
+    "acamprosate",
+    "abiraterone",
+    "pindolol",
+    "amantadine",
+    "budesonide",
+    "alvimopan",
+    "dalfampridine",
+    "nilotinib",
+    "ponatinib",
+    "clomipramine",
+    "bexagliflozin",
+    "mefenamic acid",
+    "rifabutin",
+    "fesoterodine",
+    "ulipristal",
+    "ramelteon",
+    "ketoconazole",
+    "selegiline"
   ],
   "metadata": {
     "n_train": 76,
-    "n_holdout": 71,
+    "n_holdout": 100,
     "split_method": "murcko_generic_scaffold_stratified",
     "seed": 42,
     "n_scaffolds": 101,