feat(simulation): add YAML content loader with hot-reload (#326)

LinePool system parses dialogue.yaml and monologue.yaml into indexed
BTreeMap structures. Supports 4-layer query filtering (access >
situation > trust > topic+mood) per D-028. Hot-reload via timestamp
polling every 20 ticks (dev-only). Graceful failure preserves
previous content on reload error.

30+ tests covering enum parsing, index building, query filtering,
monologue fallback, and content watching.

Ref: D-028, D-032, D-035, D-041

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

server/tests/content_loading.rs

@@ -45,7 +45,10 @@ fn discover_real_content_structure() {
     assert!(!manifest.campaigns.is_empty());
 
     // At least one district should be discovered
-    assert!(!store.districts.is_empty(), "should discover at least one district");
+    assert!(
+        !store.districts.is_empty(),
+        "should discover at least one district"
+    );
 }
 
 #[test]
@@ -298,6 +301,7 @@ fn content_plugin_loads_via_app() {
     app.add_plugins(settled_reach_server::npc::NpcPlugin);
     app.insert_resource(ContentConfig {
         content_root: root,
+        ..Default::default()
     });
     app.add_plugins(ContentPlugin);
 
@@ -353,13 +357,18 @@ fn spawn_real_content_with_relationships_and_secrets() {
         );
         npcs_with_want += 1;
     }
-    assert_eq!(npcs_with_want, 20, "All 20 NPCs should have Want components");
+    assert_eq!(
+        npcs_with_want, 20,
+        "All 20 NPCs should have Want components"
+    );
 
     // Spot-check specific Want values
     let kael_entity = registry
         .to_entity(&result.npc_ids["npc:kael-davan"])
         .unwrap();
-    let kael_want = world.get::<npc::Want>(kael_entity).expect("Kael should have Want");
+    let kael_want = world
+        .get::<npc::Want>(kael_entity)
+        .expect("Kael should have Want");
     assert_eq!(kael_want.primary, npc::WantKind::Safety);
 
     // Verify Kael has a Secret component
@@ -383,9 +392,11 @@ fn spawn_real_content_with_relationships_and_secrets() {
     let kael_kg = world
         .get::<settled_reach_server::knowledge::graph::KnowledgeGraph>(kael_entity)
         .expect("Kael should have KnowledgeGraph");
-    assert!(kael_kg.knows_fact(&settled_reach_server::knowledge::types::FactId(
-        "contraband.ring_exists".to_string()
-    )));
+    assert!(
+        kael_kg.knows_fact(&settled_reach_server::knowledge::types::FactId(
+            "contraband.ring_exists".to_string()
+        ))
+    );
 
     // Verify global RelationshipGraph was populated
     let graph = world.resource::<settled_reach_server::npc::relationships::RelationshipGraph>();
@@ -400,6 +411,8 @@ fn spawn_real_content_with_relationships_and_secrets() {
         .resource::<EntityRegistry>()
         .to_entity(&result.npc_ids["npc:nils-davan"])
         .unwrap();
-    let nils_want = world.get::<npc::Want>(nils_entity).expect("Nils should have Want");
+    let nils_want = world
+        .get::<npc::Want>(nils_entity)
+        .expect("Nils should have Want");
     assert_eq!(nils_want.primary, npc::WantKind::Power);
 }