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/content.yaml

@@ -1,7 +1,11 @@
 # Content manifest — The Settled Reach v0.1
-# The server reads this first to discover enabled districts and load order.
+# The server reads this first to discover campaigns and content layout.
+# District discovery uses glob patterns — no per-district listing needed.
 version: "0.1.0"
-districts:
-  - id: "sova-transit"
-    path: "districts/sova-transit"
+
+campaigns:
+  - id: "main"
+    path: "campaigns/main"
     enabled: true
+    discovery:
+      districts: "systems/**/districts/*/district.yaml"