Add crowd presentation, fix NPC navigation, refresh screenshots

NPC navigation (previously dead in the live game)
- Only assign NavigationAgent3D.target_position when it changes: re-assigning every
  frame invalidated the path, so get_next_path_position() kept returning the current
  point and avatars never moved.
- Follow the first path point that is closer to the destination than the avatars are.
  Nav points sit on the navmesh plane (y=0) while bodies stand at y~0.5, so the old
  3D distance test always looked "already there"; path[0] is also the old start point,
  so a naive "far enough away" pick steered backwards and oscillated.
- Fix fsm.state -> fsm.current_state in the idle-lifetime check.

Crowd presentation
- Aggressive behavior, visible weapons, and responder arrivals make idle bystanders
  stop and face the incident for 12 s; someone waiting at the entrance keeps focus.
- Panic (mood >= 0.75) walks people away from the door at 2.4 m/s, then they despawn.
- Wire reactions to EventBus.crowd_changed: CrowdSystem.apply_event() emits on the bus,
  not on its own `changed` signal (the first wiring received nothing).
- Measured a 16-NPC entrance at ~1.2 ms/frame (824 fps, vsync off), so no LOD/culling.

World and HUD
- Skyline is now a ring of four alpha-scissored planes at 200 m instead of a single
  plane; PlaneMesh defaults to horizontal, which is why the backdrop rendered as a band
  overhead. Larger ground plane, mipmapped texture, scissor threshold 0.5 (0.3 left
  mip dashes in the sky), lifted albedo so the city is not pure black.
- Flashlight aims straight ahead and lights the person/door instead of the ground.
- Shorter HUD controls line so it stops overlapping itself.

Tests, tooling, docs
- Headless suite 98 -> 105 (new test_crowd_presentation.gd, 7 tests).
- New smoke_crowd.gd: rubbernecking, panic, and flee-target sanity.
- capture_screenshots.gd starts a shift from the venue menu and stages the night set
  properly; all six README screenshots regenerated.
- README, TODO/DONE (crowd section moved), MEMORY updated. Version 0.2.4.

src/core/crowd_system.gd

@@ -45,6 +45,20 @@ func apply_event(event_type: String) -> void:
 			"event": event_type,
 		})
 
+## Presentation cue for the avatars after a crowd event (PLAN: Public Crowd
+## Reaction). "watch" = rubberneck at the incident, "flee" = move away from the
+## door, "" = no reaction. Pure so it is headless-testable.
+static func reaction_for_event(event_type: String) -> String:
+	match event_type:
+		"aggressive_behavior", "visible_weapon", "emergency_responder":
+			return "watch"
+		_:
+			return ""
+
+## True once the crowd is panicking hard enough that people should clear out.
+func should_flee() -> bool:
+	return crowd_panic
+
 func summary() -> Dictionary:
 	return {
 		"mood": mood,