fix(simulation): persist TriangleState in SaveStateV1

Triangle phase and tension were silently lost on save/load. Now
serialized as triangle_states vec in SaveStateV1, sorted by
triangle_id for determinism (D-010). Dedicated triangle entities
are respawned on load.

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

server/src/simulation/save_io.rs

@@ -16,7 +16,7 @@ use thiserror::Error;
 
 use crate::bridge::types::SaveLoadResultWire;
 use crate::bridge::types::SnapshotBuffer;
-use crate::content::template::TemplateReferenceMap;
+use crate::content::template::{TemplateReferenceMap, TriangleState};
 use crate::knowledge::graph::KnowledgeGraph;
 use crate::knowledge::registry::EntityRegistry;
 use crate::npc::Npc;
@@ -113,6 +113,13 @@ pub fn save_to_file(path: &Path, world: &mut World) -> Result<(), SaveLoadError>
         .cloned()
         .unwrap_or_default();
 
+    // Capture TriangleState components — sorted by triangle_id for determinism (D-010).
+    let mut triangle_states: Vec<TriangleState> = {
+        let mut q = world.query::<&TriangleState>();
+        q.iter(world).cloned().collect()
+    };
+    triangle_states.sort_by_key(|t| t.triangle_id.0);
+
     let state = SaveStateV1 {
         format_version: SAVE_FORMAT_VERSION,
         tick,
@@ -122,6 +129,7 @@ pub fn save_to_file(path: &Path, world: &mut World) -> Result<(), SaveLoadError>
         relationship_graph,
         npc_states,
         template_references,
+        triangle_states,
     };
 
     let bytes = state
@@ -210,6 +218,11 @@ 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);
+
+    // Restore triangle states (#250) — spawn dedicated entities for each.
+    for ts in &state.triangle_states {
+        world.spawn(ts.clone());
+    }
     {
         let mut t = world.resource_mut::<SimulationTime>();
         t.tick = state.tick;
@@ -508,6 +521,7 @@ mod tests {
             relationship_graph: RelationshipGraph::new(),
             npc_states: vec![],
             template_references: TemplateReferenceMap::default(),
+            triangle_states: vec![],
         };
         let bytes = bad_state.to_bytes().expect("serialize");
         let path = temp_path();