feat(simulation): persist template ownership and references in save state

Adds TemplateOwnership to NpcSaveState and TemplateReferenceMap to
SaveStateV1 so cross-template links survive save/load and tier
eviction (D-025, D-026). Both fields use serde(default) for backward
compatibility with existing saves.

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

server/src/simulation/save_io.rs

@@ -16,6 +16,7 @@ use thiserror::Error;
 
 use crate::bridge::types::SaveLoadResultWire;
 use crate::bridge::types::SnapshotBuffer;
+use crate::content::template::TemplateReferenceMap;
 use crate::knowledge::graph::KnowledgeGraph;
 use crate::knowledge::registry::EntityRegistry;
 use crate::npc::Npc;
@@ -105,6 +106,13 @@ pub fn save_to_file(path: &Path, world: &mut World) -> Result<(), SaveLoadError>
     npc_states.sort_by_key(|s| s.stable_id.0);
 
     let npc_count = npc_states.len();
+
+    // Capture TemplateReferenceMap if present — default to empty if not yet initialised.
+    let template_references = world
+        .get_resource::<TemplateReferenceMap>()
+        .cloned()
+        .unwrap_or_default();
+
     let state = SaveStateV1 {
         format_version: SAVE_FORMAT_VERSION,
         tick,
@@ -113,6 +121,7 @@ pub fn save_to_file(path: &Path, world: &mut World) -> Result<(), SaveLoadError>
         player_knowledge,
         relationship_graph,
         npc_states,
+        template_references,
     };
 
     let bytes = state
@@ -200,6 +209,7 @@ pub fn load_from_file(path: &Path, world: &mut World) -> Result<(), SaveLoadErro
 
     // Restore simulation resources.
     world.insert_resource(state.relationship_graph);
+    world.insert_resource(state.template_references);
     {
         let mut t = world.resource_mut::<SimulationTime>();
         t.tick = state.tick;
@@ -487,6 +497,7 @@ mod tests {
 
     #[test]
     fn load_from_file_rejects_wrong_format_version() {
+        use crate::content::template::TemplateReferenceMap;
         // Craft a save with a wrong format_version
         let bad_state = SaveStateV1 {
             format_version: 0xFF, // deliberately wrong
@@ -496,6 +507,7 @@ mod tests {
             player_knowledge: KnowledgeGraph::new(),
             relationship_graph: RelationshipGraph::new(),
             npc_states: vec![],
+            template_references: TemplateReferenceMap::default(),
         };
         let bytes = bad_state.to_bytes().expect("serialize");
         let path = temp_path();