feat(simulation): dialogue pipeline, ContentSlug, and walk-away KG recording

Implement full dialogue selection pipeline (D-028): 4-layer filtering
engine with access tier, situation derivation, trust tier, and weighted
topic+mood scoring via SimRng. Add ContentSlug component for stable
content identity across save/load. Add walk-away KG recording with
IncompleteInteraction events per D-064 three-phase consequences. Bump
protocol to v8 with DialogueResponseEvent. Fixes #305, #427, #452.

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

server/src/content/spawn.rs

@@ -32,6 +32,19 @@ use crate::simulation::interaction::Interactable;
 use crate::simulation::movement::TilePosition;
 use crate::simulation::time::DayPhase;
 
+/// Stable content identifier from YAML (e.g., "kael-davan", "sera-venn").
+///
+/// Bridges authoring identity to ECS entities. Independent of StableId —
+/// StableId is runtime entity tracking (KG references), ContentSlug is
+/// authoring/content identity (which authored NPC template). Not all entities
+/// have ContentSlugs (e.g., procedurally spawned NPCs, furniture).
+///
+/// Used by #427 (walk-away KG recording) to record interaction memory
+/// against a stable content identity rather than an Entity (which is
+/// unstable across save/load).
+#[derive(Component, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct ContentSlug(pub String);
+
 /// Result of spawning content into the ECS world.
 #[derive(Debug, Default)]
 pub struct SpawnResult {
@@ -184,7 +197,9 @@ fn spawn_npc(world: &mut World, profile: &types::NpcProfile, result: &mut SpawnR
 
     // Register in EntityRegistry for StableId mapping
     let stable_id = world.resource_mut::<EntityRegistry>().register(entity);
-    world.entity_mut(entity).insert(StableEntityId(stable_id));
+    world
+        .entity_mut(entity)
+        .insert((StableEntityId(stable_id), ContentSlug(profile.canonical_id.clone())));
 
     result
         .npc_ids
@@ -722,6 +737,26 @@ mod tests {
         assert!(!skills.combat_trained);
     }
 
+    #[test]
+    fn spawn_npc_attaches_content_slug() {
+        let mut world = create_test_world();
+        let profile = create_test_profile();
+        let mut result = SpawnResult::default();
+
+        spawn_npc(&mut world, &profile, &mut result);
+
+        let stable_id = result.npc_ids["test-npc"];
+        let entity = world
+            .resource::<EntityRegistry>()
+            .to_entity(&stable_id)
+            .unwrap();
+
+        let slug = world
+            .get::<ContentSlug>(entity)
+            .expect("ContentSlug should be attached during spawn");
+        assert_eq!(slug.0, "test-npc");
+    }
+
     #[test]
     fn spawn_npc_minimal_profile() {
         let mut world = create_test_world();