refactor(data): restructure content directory for galaxy scale

Replace flat content/districts/ with hierarchical campaign/system/
station/district structure. Path mirrors canonical IDs, enables
glob-based discovery, and is multi-campaign/DLC ready.

- git mv 46 files preserving history
- New metadata: campaign.yaml, system.yaml, station.yaml
- Rewrite content.yaml with glob-based district discovery
- Add campaign, system, station JSON schemas
- Update district schema: hierarchy fields derived from path
- Update npc-profile schema: accept district-scoped IDs
- Add TODO to 17 dialogue/monologue pool files for generator revision
- Update _meta/README.md with new hierarchy documentation

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

content/_schema/district.schema.json

@@ -2,15 +2,15 @@
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "$id": "district.schema.json",
   "title": "District Metadata",
-  "description": "District definition file — one per district directory (D-036).",
+  "description": "District definition file — one per district directory (D-036). Identity derived from directory path.",
   "type": "object",
-  "required": ["display_name", "system", "station", "district", "description", "locations", "npc_count"],
+  "required": ["display_name", "description", "locations", "npc_count"],
   "additionalProperties": false,
   "properties": {
     "canonical_id": {
       "type": "string",
       "pattern": "^[a-z]+\\.[a-z]+\\.[a-z-]+$",
-      "description": "Optional — derived from directory path at load time. If present, must match {system}.{station}.{district}."
+      "description": "Deprecated — derived from directory path at load time. If present, must match {system}.{station}.{district}."
     },
     "display_name": {
       "type": "string",
@@ -18,15 +18,18 @@
     },
     "system": {
       "type": "string",
-      "pattern": "^[a-z]+$"
+      "pattern": "^[a-z]+$",
+      "description": "Deprecated — derived from directory path."
     },
     "station": {
       "type": "string",
-      "pattern": "^[a-z]+$"
+      "pattern": "^[a-z]+$",
+      "description": "Deprecated — derived from directory path."
     },
     "district": {
       "type": "string",
-      "pattern": "^[a-z-]+$"
+      "pattern": "^[a-z-]+$",
+      "description": "Deprecated — derived from directory path."
     },
     "description": {
       "type": "string",