Capture and surface game server exit codes in LocalMultiplayerAgent

[Copilot]

Game server exit codes were silently discarded. For containers, the code logged the exit code but never returned it. For processes, exit codes were never captured at all. This made it impossible to diagnose crashes or non-zero exits from the game server.

Interface changes

• IProcessWrapper.WaitForProcessExit: void → int
• ISessionHostRunner.WaitOnServerExit: Task → Task<int>
• BaseSessionHostRunner abstract signature updated accordingly

ProcessWrapper: retain Process references to avoid GetProcessById pitfalls

Process.GetProcessById(pid) throws ArgumentException if the process has already exited, and is subject to PID reuse races. Both make exit code retrieval unreliable for short-lived or crashing servers.

ProcessWrapper now tracks started Process objects in a ConcurrentDictionary and retrieves them by ID in WaitForProcessExit, falling back to GetProcessById only for externally-started processes.

if (!_trackedProcesses.TryRemove(id, out Process process))
{
    process = Process.GetProcessById(id);
}
process.WaitForExit();
return process.ExitCode;

Runner implementations

• ProcessRunner — returns and logs exit code from ProcessWrapper
• DockerContainerEngine — returns ContainerWaitResponse.StatusCode (was already captured, just discarded)

MultiplayerServerManager

Captures the exit code and writes it to both logger and console:

Game server exited with exit code 1.

[Copilot]

Pull request overview

This PR updates the LocalMultiplayerAgent/VmAgent runner abstractions to capture and propagate game server exit codes (both process and container based), so crashes/non-zero exits are surfaced to logs/console instead of being silently discarded.

Changes:

• Updated runner/process-wrapper interfaces to return exit codes (WaitForProcessExit → int, WaitOnServerExit → Task<int>).
• Added process tracking in ProcessWrapper to reliably retrieve exit codes without GetProcessById races.
• Plumbed exit codes through ProcessRunner and DockerContainerEngine to MultiplayerServerManager for logging/console output.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
VmAgent.Core/Interfaces/ProcessWrapper.cs	Track started Process instances and return ExitCode from WaitForProcessExit.
VmAgent.Core/Interfaces/IProcessWrapper.cs	Interface updated to return an exit code from WaitForProcessExit.
VmAgent.Core/Interfaces/ProcessRunner.cs	Return/log process exit code from WaitOnServerExit.
VmAgent.Core/Interfaces/DockerContainerEngine.cs	Return/log container exit code from WaitOnServerExit (previously logged only).
VmAgent.Core/Interfaces/ISessionHostRunner.cs	Interface updated: WaitOnServerExit now returns Task<int>.
VmAgent.Core/Interfaces/BaseSessionHostRunner.cs	Abstract signature updated to Task<int> WaitOnServerExit(...).
LocalMultiplayerAgent/MultiplayerServerManager.cs	Capture returned exit code and write it to logger + console.

Comments suppressed due to low confidence (1)

VmAgent.Core/Interfaces/ProcessWrapper.cs:22

• Now that ProcessWrapper retains Process objects in _trackedProcesses, Kill(int id) should prefer the tracked Process reference (and remove/dispose it) instead of calling Process.GetProcessById. Using GetProcessById after the original process has exited can hit PID reuse and potentially kill an unrelated process; tracking was introduced specifically to avoid this class of race.

        private readonly ConcurrentDictionary<int, Process> _trackedProcesses = new ConcurrentDictionary<int, Process>();

        public void Kill(int id)
        {
            try
            {
                Process process = Process.GetProcessById(id);
                process.Kill(true);
            }