ai-battle: support team assignment (--teams) and establish team start-pacts

[FlexApex]

ai-battle: support team assignment (--teams) and establish team start-pacts

Builds on #1949 (uses its HeadlessGame). Two commits:

1. --teams option for team assignment

Adds a --teams option to the headless ai-battle harness so the AI can be
verified under real team rules instead of a free-for-all:

ai-battle -m Map.swd --ai aijh --ai aijh --ai aijh --ai aijh --teams "0,1;2,3"

Groups are separated by ;, player indices by ,. The first group becomes
Team1, the second Team2, and so on; unlisted players stay teamless. The
assignment is threaded through HeadlessGame into GeneratePlayerInfo, which
sets PlayerInfo::team.

2. Establish team start-pacts in HeadlessGame to match GameClient (avoid desyncs in replays)

GameClient::StartGame calls GamePlayer::MakeStartPacts() for every player on
a fresh map, creating the ally + non-aggression pacts that bind a team together.
HeadlessGame never did this, so a recorded ai-battle with teams had no pacts:
GamePlayer::IsAttackable() returned true for teammates and the AIs attacked
their own team. On replay GameClient does set up the pacts, so the recorded
inter-team attack commands hit allied players and were resolved differently —
producing an object-count divergence (replay desync) without any RANDOM
divergence.

MakeStartPacts() early-returns for Team::None, so the call is a no-op until
players are actually assigned to teams via --teams. Together with the
MapLoader::SetupResources() call already in HeadlessGame, this makes the
headless world setup match the GameClient replay path.

Note

• Depends on Fix and extend AI-Battle #1949 — best merged after it (or rebased onto master once Fix and extend AI-Battle #1949 lands).