feat(data): add content schema definitions

JSON Schema (draft 2020-12) for content validation: district,
location, npc-profile, dialogue-pool, monologue-pool, triangle,
routine, and fact-catalog. NPC schema uses if/then conditional
for FRIEND pattern validation. Implements ticket #386.

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

content/_schema/district.schema.json

@@ -0,0 +1,49 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "district.schema.json",
+  "title": "District Metadata",
+  "description": "District definition file — one per district directory (D-036).",
+  "type": "object",
+  "required": ["canonical_id", "display_name", "system", "station", "district", "description", "locations", "npc_count"],
+  "additionalProperties": false,
+  "properties": {
+    "canonical_id": {
+      "type": "string",
+      "pattern": "^[a-z]+\\.[a-z]+\\.[a-z-]+$",
+      "description": "Canonical ID in format {system}.{station}.{district}"
+    },
+    "display_name": {
+      "type": "string",
+      "minLength": 1
+    },
+    "system": {
+      "type": "string",
+      "pattern": "^[a-z]+$"
+    },
+    "station": {
+      "type": "string",
+      "pattern": "^[a-z]+$"
+    },
+    "district": {
+      "type": "string",
+      "pattern": "^[a-z-]+$"
+    },
+    "description": {
+      "type": "string",
+      "minLength": 1
+    },
+    "locations": {
+      "type": "array",
+      "items": {
+        "type": "string",
+        "pattern": "^[a-z][a-z0-9-]*$"
+      },
+      "minItems": 1,
+      "uniqueItems": true
+    },
+    "npc_count": {
+      "type": "integer",
+      "minimum": 0
+    }
+  }
+}