feat(arena-tk2): SoloDefaultsToScripted config flag for dev convenience

Adds BattleNodeOptions.SoloDefaultsToScripted (default false). When true,
the TK2 do_matching controller treats every solo poll as if ?scripted=1
were passed and returns a Scripted 3004 match immediately — useful for
the live client (which can't append query params) to drive the scripted
bot without needing a second player.

Toggle via "BattleNode:SoloDefaultsToScripted" in appsettings*.json
(Program.cs now binds the BattleNode section over the AddBattleNode
defaults). Turn off to test real PvP with two clients.

Trade-off documented on the option: while on, two simultaneous pollers
each get their own Scripted match instead of pairing, so PvP is
effectively disabled until the flag is flipped.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/appsettings.Development.json

@@ -4,5 +4,8 @@
       "Default": "Information",
       "Microsoft.AspNetCore": "Warning"
     }
+  },
+  "BattleNode": {
+    "SoloDefaultsToScripted": false
   }
 }