Add Discord SDK crash fallback

[mindless2831]

Summary

Adds a Discord SDK crash fallback for game launch.

Fixes #2708.

What changed

This PR adds two protections for users affected by native Discord SDK crashes during Nitrox startup:

• Adds a launcher option to enable/disable Discord integration.
• Adds a launch flag that lets the client skip Nitrox Discord integration entirely.
• Skips creating DiscordClient when Discord integration is disabled.
• Guards Rich Presence calls so they are not invoked when Discord integration is disabled.
• Monitors the launched Subnautica process briefly after startup.
• If Subnautica exits during the observation window and Player.log contains the known Discord SDK crash signatures, the launcher relaunches Subnautica once with Discord integration disabled.
• Shows a launcher warning explaining that Discord integration was disabled for the retry.

Why

The crash in #2708 occurs inside the native Discord SDK path around Rich Presence initialization/update:

• discord_game_sdk
• DiscordClient.InitializeRPMenu
• DiscordClient.UpdateActivity
• DiscordGameSDKWrapper.ActivityManager.UpdateActivity

Because this is a native crash, managed try/catch inside the client is not reliable. The safer fallback is to relaunch without initializing Discord integration.

Testing

Tested manual Discord integration toggle:

• With Discord integration enabled, Discord shows Nitrox Rich Presence / main menu activity.
• With Discord integration disabled, Discord only shows normal Subnautica activity and Nitrox does not start its Discord client.
• Game log confirms disabled launches with:
  [Discord] Discord integration disabled by launch argument

Tested fallback behavior using a local test-only forced detection path:

• Initial launch starts with Discord integration enabled.
• Simulated Discord crash detection triggers after game exit during the observation window.
• Launcher relaunches Subnautica with Discord integration disabled.
• Relaunched game logs:
  [Discord] Discord integration disabled by launch argument

The forced test hook was removed before this PR.

Also tested normal early game exit without a current Discord crash signature; the launcher does not relaunch.

[github-actions]

Test Results

255 tests  ±0   252 ✅ ±0   18s ⏱️ -5s
  1 suites ±0     3 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit b98bd95. ± Comparison against base commit a89227d.