refactor(simulation): address PR #72 review suggestions

- Hoshe #3: replace O(n²) Vec scan in fallback NPC assignment with
  BTreeSet; prevent same NPC assigned to two roles in one triangle
- Hoshe #4: add From impls for RoleId, TriangleId, StableId, and
  TriangleCrisisEventWire — eliminate fragile .0 access on newtypes
- Hoshe #5: consolidate near-identical unit tests with integration
  counterparts — keep only unique tests in #[cfg(test)] module
- Tyre #3: replace O(N*M) scan in apply_resolve_triangle with
  BTreeMap<TriangleId, Entity> index for O(1) per-command lookup
- Tyre #4: document &mut World on generate_intra_template_triangles
- Observer snapshot uses TriangleCrisisEventWire::from instead of
  manual field mapping

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

server/src/knowledge/types.rs

@@ -18,6 +18,12 @@ use crate::simulation::movement::TilePosition;
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
 pub struct StableId(pub u64);
 
+impl From<StableId> for u64 {
+    fn from(id: StableId) -> Self {
+        id.0
+    }
+}
+
 /// Typed fact identifier for non-entity knowledge.
 /// Format: "category.topic" (e.g., "contraband.ring_exists").
 /// Lexicographic ordering in BTreeMap provides deterministic iteration.