feat(data): create content/ directory skeleton

Scaffolds the full content directory structure per D-057 spec:
district-as-atomic-pack layout with Sova Transit as the first
district. Includes 17 NPC stubs, 3 locations, 5 triangles,
9 dialogue pools, 8 monologue pools, routines, 7 factions,
7 knowledge catalogs, 8 enum definitions, and global region.
Implements ticket #385.

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

content/content.yaml

@@ -0,0 +1,7 @@
+# Content manifest — The Settled Reach v0.1
+# The server reads this first to discover enabled districts and load order.
+version: "0.1.0"
+districts:
+  - id: "sova-transit"
+    path: "districts/sova-transit"
+    enabled: true