fix(jupiter): set jovian.steam.desktopSession to gamescope-wayland

[johnae]

Summary

• world upgrade on jupiter fails to evaluate because jovian.steam.desktopSession is null while autoStart = true. The jovian autostart module interpolates ${cfg.desktopSession} into a systemd ExecStart string, triggering cannot coerce null to a string.
• Set it to "gamescope-wayland" to keep current behavior (matches the in-tree warning's recommendation).

Test plan

• nix eval .#nixosConfigurations.jupiter.config.system.build.toplevel.drvPath succeeds locally
• world upgrade on jupiter once merged

[claude]

Claude finished @johnae's task —— View job

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PR Review: Fix jovian.steam.desktopSession Configuration

Todo List

• Read the changed file to understand the fix
• Analyze the code change in context
• Review for code quality and best practices
• Check for potential bugs or issues
• Consider performance implications
• Assess security concerns
• Evaluate test coverage
• Provide comprehensive review feedback

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Review Summary

✅ The fix is correct and necessary. This one-line change properly addresses the null coercion error by explicitly setting jovian.steam.desktopSession to "gamescope-wayland".

Code Quality and Best Practices

Positive aspects:

• The fix is minimal and targeted, changing only what's necessary
• The value "gamescope-wayland" aligns with the Jovian NixOS module's recommended default for Steam Deck-like devices
• The configuration maintains consistency with the existing Jovian Steam setup

Suggestions:

• Consider documenting why this specific desktop session is chosen (e.g., add a comment explaining it's the recommended default for gaming-focused setups)

Potential Bugs or Issues

✅ No bugs identified. The fix correctly resolves the null interpolation issue that was breaking the systemd service configuration.

The error occurred because:

1. jovian.steam.autoStart = true enables the auto-start systemd service
2. The service's ExecStart line interpolates ${cfg.desktopSession}
3. Without an explicit value, desktopSession defaults to null, causing the "cannot coerce null to a string" error

Performance Considerations

✅ No performance impact. This is a configuration value that determines which desktop session to launch. The choice of gamescope-wayland is appropriate for a gaming-focused system as it provides:

• Better performance for gaming workloads
• Wayland compatibility
• Steam Deck-like experience

Security Concerns

✅ No security issues identified. The configuration change:

• Uses a standard, well-tested desktop session
• Doesn't introduce any privilege escalation
• Maintains the existing security boundaries

Test Coverage

Current testing:

• ✅ Local evaluation passes: nix eval .#nixosConfigurations.jupiter.config.system.build.toplevel.drvPath
• ⏳ Actual deployment test pending after merge

Recommendations:

• The test plan is appropriate for this change
• Consider adding this configuration requirement to any existing Jovian setup documentation to prevent similar issues in the future

Conclusion

This is a well-targeted, necessary fix that resolves a blocking evaluation error. The chosen value is appropriate for the gaming-focused nature of the Jupiter system configuration. The PR should be merged to unblock world upgrade operations on the jupiter host.