Phase 7: netfox + godot-jolt stack upgrade

Stack installed:
- netfox v1.35.3 (core + extras + noray + internals)
- godot-jolt v0.16.0-stable

Architecture:
- Server: ENet transport (works headless, no netfox deps)
- Client/Editor: netfox rollback (RollbackSynchronizer, TickInterpolator)

New/modified:
- docs/migration-netfox-plan.md — migration architecture
- scripts/network/network_manager.gd — netfox-aware ENet fallback
- scripts/network/player.gd — clean base player
- client/characters/player_netfox.gd — rollback player w/ WeaponManager
- client/characters/input/player_net_input.gd — BaseNetInput subclass
- client/characters/character/fps_character_controller.gd — netfox input feed
- client/weapons/ — weapon data, registry, TacticalWeaponHitscan, WeaponManager
- client/scripts/round_replicator.gd — client-side round state bridge
- server/scripts/round_manager.gd — improved state machine
- server/scripts/plugin_api/plugin_manager.gd — refined plugin system
- config: enemy_tag, ally_tag for meatball targeting

Removed: old C++ SimulationServer GDExtension (replaced by netfox rollback)

gdextension.disabled/simulation/gdextension/simulation.gdextension.disabled

@@ -0,0 +1,10 @@
+[configuration]
+entry_symbol = "gdextension_entry"
+compatibility_minimum = "4.2"
+
+[libraries]
+linux.x86_64 = "res://gdextension/bin/linux/libsimulation.so"
+linux.arm64 = "res://gdextension/bin/linux/libsimulation.so"
+windows.x86_64 = "res://gdextension/bin/windows/libsimulation.dll"
+macos.x86_64 = "res://gdextension/bin/macos/libsimulation.dylib"
+macos.arm64 = "res://gdextension/bin/macos/libsimulation.dylib"

gdextension.disabled/simulation/gdextension/simulation.gdextension.uid

@@ -0,0 +1 @@
+uid://kl43xi0ixseg