fix: Apply mission_hub exit pattern to Netherton and Haxolottle

Applied the same conversation flow fix from chen_hub.ink to the other
two NPCs. Exit options now properly preserve state at mission_hub while
closing the conversation.

Pattern Applied:
  #end_conversation
  -> mission_hub

Instead of:
  #end_conversation
  -> DONE

This ensures:
1. Exit options close the conversation minigame (#end_conversation tag)
2. Story state is preserved AT mission_hub (not DONE)
3. Next conversation resumes from mission_hub with all options available
4. Player can have multiple conversation topics before choosing to exit

Files Updated:
- netherton_hub.ink (2 exit options)
- haxolottle_hub.ink (2 exit options)

Recompiled all hub JSON files.

All three NPCs now have consistent conversation flow behavior.

scenarios/ink/haxolottle_hub.ink

@@ -132,7 +132,7 @@ EXTERNAL operational_stress_level()     // LOCAL - How stressed the current situ
 + {mission_phase() == "active"} [That's all I needed. Thanks, Hax.]
     Haxolottle: Roger. I'm monitoring your situation. Call if you need anything. Stay safe out there.
     #end_conversation
-    -> DONE
+    -> mission_hub
 
 + [That's all for now]
     {
@@ -144,7 +144,7 @@ EXTERNAL operational_stress_level()     // LOCAL - How stressed the current situ
             Haxolottle: Okay. Talk later!
     }
     #end_conversation
-    -> DONE
+    -> mission_hub
 
 // ===========================================
 // HELPER FUNCTION - Check for available personal topics

scenarios/ink/netherton_hub.ink

@@ -107,7 +107,7 @@ EXTERNAL mission_phase()                // LOCAL - Phase of current mission ("pr
 + {mission_phase() == "active"} [That's all I needed, Director]
     Netherton: Understood. Execute the mission. Report any developments.
     #end_conversation
-    -> DONE
+    -> mission_hub
 
 + [That will be all, Director]
     {
@@ -119,7 +119,7 @@ EXTERNAL mission_phase()                // LOCAL - Phase of current mission ("pr
             Netherton: Dismissed.
     }
     #end_conversation
-    -> DONE
+    -> mission_hub
 
 // ===========================================
 // HELPER FUNCTION - Check for available personal topics