docs(eval): enforce min-sample gates in canary artifacts and decision log

docs/plans/artifacts/pi_embedded_eval_window_a_2026-02-24.json

@@ -1,5 +1,5 @@
 {
-  "generated_at": "2026-02-24T06:28:12.014Z",
+  "generated_at": "2026-02-24T06:33:31.111Z",
   "event_count": 45,
   "filters": {},
   "options": {
@@ -73,12 +73,12 @@
     },
     "fallback_categories": [
       {
-        "category": "loaded pi module does not expose a supported session factory (expected one of: c",
+        "category": "empty_assistant_text",
         "count": 1,
         "pct": 50
       },
       {
-        "category": "pi agent runtime produced no assistant text",
+        "category": "pi_module_interface",
         "count": 1,
         "pct": 50
       }
@@ -97,6 +97,24 @@
   "gate": {
     "pass": false,
     "criteria": [
+      {
+        "criterion": "Minimum target routes",
+        "pass": true,
+        "actual": "8",
+        "threshold": ">= 8"
+      },
+      {
+        "criterion": "Minimum baseline routes",
+        "pass": true,
+        "actual": "2",
+        "threshold": ">= 2"
+      },
+      {
+        "criterion": "Minimum target external attempts",
+        "pass": true,
+        "actual": "8",
+        "threshold": ">= 8"
+      },
       {
         "criterion": "Completion rate delta (target - baseline)",
         "pass": true,