Skip SaveAndReload in HostServer when hosting from replay

[sviyh]

Summary

• HostUtil.CreateGameData always calls SaveLoad.SaveAndReload. The reload step is needed for the SP-host path (canonicalizes MP-injected state) but is wasted work for the replay-host path (state was just deserialized from disk).
• The wasted reload introduces a Verse.Rand stream perturbation: mod-side spawn-time graphic randomization (e.g. AdaptiveStorage Framework's ThingGrid.RegisterInCell transpiler hook) consumes Rand inside SeedMapFinalizeLoading's seeded scope at different stream positions on the host's in-process reload vs the client's fresh-process load. Result: divergent RoomTempTracker.equalizeCells orderings → temperature drift → desync at the next FreezeManager.DoIceMelting Rand.Chance boundary (~120 ticks later).
• Fix: pass fromReplay to CreateGameData. Use SaveLoad.SaveGameData (save without reload) on the replay path. SP-host path unchanged.

Investigation

Probe instrumentation captured the divergence:

• Host load count per Map.FinalizeLoading event:
  • tick 9954061 (replay file load via Root_Play.Start): 42 regens, byte-identical to client
  • tick 9954062 (SaveAndReload via HostUtil.CreateGameData): 84 regens, divergent shuffle output
  • tick 9956175 (SaveAndReload via CreateJoinPointAndSendIfHost): also asymmetric, but fires after the desync is already manifest
• WallEqProbe captured runtime divergence at tick 9954127 — host's equalizeCells for room r=45 came from the SaveAndReload's shuffle output, client's from the fresh-process load.
• RandSeedProbe captured the offending Rand consumer: AdaptiveStorage's Graphic_Random.get_MatSingle chain via the ThingGrid.RegisterInCell transpiler hook on every item spawn during Map.FinalizeLoading.

Test plan

• Build clean Release DLL
• Deploy to Workshop path (D:\Steam\steamapps\workshop\content\294100\2606448745\1.6\AssembliesCustom\)
• Restore stock MP-Compat to isolate the MP fix in test
• Replay-host repro: load the same MP save that previously desynced at tick 9954128, host it, let client join. Expect: no desync past the prior divergence point.
• SP-host regression: load a SP save, host MP, let client join. Expect: state stays canonical (SaveAndReload still runs in this path).
• Single-player smoke test: confirm no SP behaviour change (the gate is on fromReplay which only matters when hosting MP).

Notes

• Does not address Load Seed RoomTempTracker.RegenerateEqualizeCells with per-room deterministic state #3 (auto-generated join-point on client connect). That fires after the host has been alive for some time, and SaveAndReload there serves a different purpose (capture transient in-memory state for client snapshot). Left untouched.
• Fixes the immediate desync class for replay-host without requiring per-mod compat patches.