rendering: fix WMO portal culling and chat message format

- wmo_renderer: pass character position (not camera position) to portal
  visibility traversal — the 3rd-person camera can orbit outside a WMO
  while the character is inside, causing interior groups to cull; render()
  now accepts optional viewerPos that defaults to camPos for compatibility
- renderer: pass &characterPosition to wmoRenderer->render() at both
  main and single-threaded call sites; reflection pass keeps camPos
- renderer: apply mount pitch/roll to rider during all flight, not just
  taxiFlight_ (fixes zero rider tilt during player-controlled flying)
- game_screen: format SAY/YELL/WHISPER/EMOTE using WoW-style "Name says:"
  instead of "[SAY] Name:" bracket prefix

include/rendering/wmo_renderer.hpp

@@ -150,7 +150,8 @@ public:
      */
     /** Pre-update mutable state (frame ID, material UBOs) on main thread before parallel render. */
     void prepareRender();
-    void render(VkCommandBuffer cmd, VkDescriptorSet perFrameSet, const Camera& camera);
+    void render(VkCommandBuffer cmd, VkDescriptorSet perFrameSet, const Camera& camera,
+                const glm::vec3* viewerPos = nullptr);
 
     /**
      * Initialize shadow pipeline (Phase 7)