Cleanup: remove legacy IMGUI ConnectionUI + crash-recovery scenes

Delete the NetConnectionUI GameObject from Game/DevSandbox/SampleScene + ConnectionUI.cs (the UITK frontend menu owns Host/Join+IP now); repoint 4 stale doc-comments (GameBootstrap done in commit C; DebugOverlay/ConnectionConfig/EditorAutoHostSystem here) to MainMenuController/WorldLauncher; remove the Assets/_Recovery crash-recovery scenes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scenes/SampleScene.unity

@@ -367,51 +367,6 @@ Transform:
   m_CorrespondingSourceObject: {fileID: 4419796514499596, guid: c444ce6e54943f64a895431df8872a52, type: 3}
   m_PrefabInstance: {fileID: 105756304}
   m_PrefabAsset: {fileID: 0}
---- !u!1 &121227139
-GameObject:
-  m_ObjectHideFlags: 0
-  m_CorrespondingSourceObject: {fileID: 0}
-  m_PrefabInstance: {fileID: 0}
-  m_PrefabAsset: {fileID: 0}
-  serializedVersion: 6
-  m_Component:
-  - component: {fileID: 121227141}
-  - component: {fileID: 121227140}
-  m_Layer: 0
-  m_Name: NetConnectionUI
-  m_TagString: Untagged
-  m_Icon: {fileID: 0}
-  m_NavMeshLayer: 0
-  m_StaticEditorFlags: 0
-  m_IsActive: 1
---- !u!114 &121227140
-MonoBehaviour:
-  m_ObjectHideFlags: 0
-  m_CorrespondingSourceObject: {fileID: 0}
-  m_PrefabInstance: {fileID: 0}
-  m_PrefabAsset: {fileID: 0}
-  m_GameObject: {fileID: 121227139}
-  m_Enabled: 1
-  m_EditorHideFlags: 0
-  m_Script: {fileID: 11500000, guid: 977a7574cf6ff4898b7e9db6c21368f9, type: 3}
-  m_Name: 
-  m_EditorClassIdentifier: ProjectM.Client::ProjectM.Client.ConnectionUI
-  _port: 7979
---- !u!4 &121227141
-Transform:
-  m_ObjectHideFlags: 0
-  m_CorrespondingSourceObject: {fileID: 0}
-  m_PrefabInstance: {fileID: 0}
-  m_PrefabAsset: {fileID: 0}
-  m_GameObject: {fileID: 121227139}
-  serializedVersion: 2
-  m_LocalRotation: {x: 0, y: 0, z: 0, w: 1}
-  m_LocalPosition: {x: 0, y: 0, z: 0}
-  m_LocalScale: {x: 1, y: 1, z: 1}
-  m_ConstrainProportionsScale: 0
-  m_Children: []
-  m_Father: {fileID: 0}
-  m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
 --- !u!4 &123327809 stripped
 Transform:
   m_CorrespondingSourceObject: {fileID: 4288372421065824, guid: 94634f97a9c7b83498a8e59c7c8f115b, type: 3}
@@ -5185,7 +5140,6 @@ SceneRoots:
   - {fileID: 832575519}
   - {fileID: 1314640900}
   - {fileID: 833091047}
-  - {fileID: 121227141}
   - {fileID: 228729546}
   - {fileID: 1736670160}
   - {fileID: 1116745582}