Prototype 0.0.52 — platoon support and history spacing repair

• Regular random-battle platoons are an intentional supported lobby context, identified through PREBATTLE_TYPE.SQUAD; Stronghold retains its dedicated watcher lifecycle.
• The history panel now labels its roster context (Skirmish roster or Platoon roster). Platoon lookup is gated until every occupied member has selected the same supported Tier VI, VIII, or X vehicle.
• Fixed the Vehicles shown …Heavy concatenation: the count remains in the fixed header and the scrolling body begins below a 16 px gap.
• Battle, post-battle, special-mode, training, tournament, and enemy roster contexts remain unsupported.