fix(simulation): address PR #55 review — stale comment, range, duplication, docs

- Fix protocol version comment (12 → 13) in ObserverSnapshot doc
- Widen Want intensity range from 3..=9 to 1..=10 to match spec and test
- Replace duplicated pool selection in trigger_recognition_monologue with
  call to select_pool_line helper (~50 lines removed)
- Document NaiveSpatialIndex migration cost for grid/quadtree swap
- Remove misleading Default derive from TellCategory (Nervous is not a
  sensible default for neutral NPCs)
- Add caller invariant doc on generate_npc (no TilePosition spawned)

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

server/src/npc/generate.rs

@@ -149,7 +149,7 @@ fn pick_combat_style(idx: usize) -> CombatStyle {
 
 fn gen_want(rng: &mut SimRng, role: &RoleDefinition) -> Want {
     let kind_idx = rng.rng.random_range(0..9_usize);
-    let intensity = rng.rng.random_range(3_u8..=9);
+    let intensity = rng.rng.random_range(1_u8..=10);
     Want {
         primary: pick_want_kind(kind_idx),
         intensity,
@@ -421,6 +421,11 @@ fn gen_skills(rng: &mut SimRng, role: &RoleDefinition) -> (SkillSet, Option<Comb
 /// Spawns the entity into `world` with all 10 D-024 axis components.
 /// All randomness flows through `rng` — deterministic for a fixed seed (D-010).
 ///
+/// **Caller invariant:** The spawned entity does NOT include `TilePosition`
+/// or `ActiveSim`. The caller must place the NPC in the world (add
+/// `TilePosition`, register in `EntityRegistry`, and assign a simulation
+/// tier) after generation.
+///
 /// Returns the newly spawned `Entity` ID.
 pub fn generate_npc(role: &RoleDefinition, world: &mut World, rng: &mut SimRng) -> Entity {
     // Generate all axes before spawning to keep the borrow checker happy.

server/src/npc/tell_state.rs

@@ -35,10 +35,9 @@ use crate::simulation::tier::ActiveSim;
 ///
 /// Derived each tick from NPC simulation state — not authored per NPC.
 /// Five categories correspond to the D-024 tell taxonomy.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default, Serialize, Deserialize)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
 pub enum TellCategory {
     /// NPC exhibits nervous behaviour: Major secret + stress exceeds half of threshold.
-    #[default]
     Nervous,
     /// NPC exhibits angry behaviour: low contentment and Hostile mood.
     Angry,