feat(simulation): NPC mood state machine (#323, D-024, D-035)

8-state NPC mood FSM driven by stress, time of day, and interaction events.
Adds MoodState component, derive_mood() pure function, and update_mood() Bevy
system wired into NpcPlugin. Adds Focused as 9th Mood content tag (D-035
Sprint 8 amendment). Syncs CurrentMood for Layer 4 dialogue selection.

31 unit tests covering priority ordering, boundary conditions, and system
integration. All random values route through SimRng (D-010 determinism).
No floats. No HashMap.

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

server/src/npc/mod.rs

@@ -2,6 +2,7 @@
 // Implements D-024: 10-axis NPC model + CombatCapability component
 // Background tier state machines for schedule, mood, relationships, job
 
+pub mod mood;
 pub mod relationships;
 pub mod routine;
 
@@ -24,8 +25,13 @@ impl Plugin for NpcPlugin {
             .init_resource::<routine::PreviousDayPhase>()
             .add_systems(
                 Update,
-                routine::check_phase_transition
-                    .before(crate::simulation::pathfinding::compute_paths),
+                (
+                    routine::check_phase_transition
+                        .before(crate::simulation::pathfinding::compute_paths),
+                    mood::update_mood
+                        .after(routine::check_phase_transition)
+                        .before(crate::simulation::dialogue::process_talk_interaction),
+                ),
             );
 
         tracing::debug!("NpcPlugin initialized");