Improve Linux runtime and collision compatibility

[bobmoser76]

Summary:

• retain and use the loaded world collision-model handle for world traces
• make end-level activation null-safe and reduce noisy collision/light diagnostics
• detect Linux VRAM through DRM sysfs with the archived cvar as fallback
• handle network-interface enumeration failures without aborting startup

Validation:

• fresh Meson debug build with the native Linux platform backend
• client, dedicated server, and unified game module linked successfully
• git diff --check