Fix native Linux runtime for sbox-server

[joshuascript]

Minimum changes for sbox-server to run natively

Result

Caveats
If a LibSkia Error is thrown: Both libskiasharp.so and harfbuzz.so need to be moved to the bin/managed folder manually for this to work. Typically the Windows-only DLLs sit in this same directory, but on Linux they are generated in linuxsteamrt64 and are currently unreachable by the engine.

A workaround was introduced that extends the lifetime of the marshaled struct and prevents native use-after-free. Initializing ClientInfo structs would cause a SIGSEGV error. When going over the gdb log, it appears the datafields became corrupted during its runtime. This issue may exist on Windows and was behaving differently. Debug traces can be provided upon request for the SIGSEGV. The ClientInfo struct seems to only exist for the lifetime of the method call, and is dereferenced later. The workaround is not a long-term fix, but maybe it can provide insight on what is actually happening to a developer snazzier than me.

This also cannot use System.Speech, it is Windows only, so it is stubbed out for any Linux runtimes.

Let me know if this helps or if I am barking up the wrong tree. There are negative implications to System.Speech not being available on a Linux-only server system. Do we think Proton is better for servers?

** may need ffmpeg8 installed to work

• Joshua

[DrakeFruit]

🙏

[Copilot]

Pull request overview

This PR implements minimum changes required to run sbox-server natively on Linux. The changes address Linux-specific filesystem case sensitivity, platform-specific API availability, and native interop marshaling issues.

Changes:

• Capitalized "assets" to "Assets" throughout the codebase to properly handle Linux case-sensitive filesystems
• Added conditional compilation directives to exclude Windows-only System.Speech functionality on non-Windows platforms
• Implemented platform-specific path handling in LocalFileSystem to preserve case sensitivity on non-Windows systems
• Added interop workaround for CMaterialSystem2AppSystemDict creation on Linux to prevent native use-after-free errors

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
engine/Sandbox.GameInstance/GameInstanceDll.cs	Updated asset paths to use capital "Assets" and wrapped Speech.Recognition.Reset() in Windows-only conditional compilation
engine/Sandbox.Filesystem/LocalFileSystem.cs	Added platform check to preserve path case sensitivity on non-Windows systems
engine/Sandbox.Engine/Systems/Filesystem/EngineFileSystem.cs	Updated all asset folder references from "assets" to "Assets" for Linux case sensitivity
engine/Sandbox.Engine/Systems/Audio/Speech/Speech.Synthesis.cs	Wrapped entire file in Windows conditional compilation since System.Speech is Windows-only
engine/Sandbox.Engine/Systems/Audio/Speech/Speech.Recognition.cs	Wrapped entire file in Windows conditional compilation since System.Speech is Windows-only
engine/Sandbox.Engine/Core/Bootstrap.cs	Updated asset download folder path to use capital "Assets"
engine/Sandbox.AppSystem/AppSystem.cs	Added platform-specific logic to use workaround for CMaterialSystem2AppSystemDict creation on Linux to prevent native marshaling issues

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[Copilot]

The CreateAppSystemWithInteropWorkaround method has a memory leak. The pWindowTitle field in the MaterialSystem2AppSystemDictCreateInfo struct is allocated by ToMaterialSystem2AppSystemDictCreateInfo using Marshal.StringToHGlobalAnsi, but this memory is never freed. You should free this allocation after the native call completes, or ensure that the native code takes ownership of the memory.

[joshuascript]

I tried to fix the formatting and it went nuts on me. You can see the most recent commit and get the actual changes. I'll try again on Monday when I'm off of work.

[joshuascript]

PR updated to latest version