fix(api): constrain disposition_overrides keys; close docker paper cuts

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/schemas/origin.schema.json

@@ -20,6 +20,7 @@
     "opening_facts": { "type": "array", "items": { "type": "string", "minLength": 1 } },
     "disposition_overrides": {
       "type": "object",
+      "propertyNames": { "pattern": "^[a-z0-9_]+$" },
       "additionalProperties": { "type": "integer", "minimum": -100, "maximum": 100 }
     },
     "inventory_grants": {