steamcmd Linux installation fixes

[et-nik]

No description provided.

[Copilot]

Pull request overview

This PR fixes Linux installation issues with steamcmd by ensuring that, when the daemon runs as root but executes steamcmd under an unprivileged su_user, steamcmd can still self-update and write into its own directory. It introduces a new osowner.ApplyGroupSharedRecursive helper that applies setgid + group rwx/rw to a shared directory, wires it into the steam install path, configures the executor to run with the right working directory and HOME, and preserves supplementary groups in the dropped-privilege child.

Changes:

• Added ApplyGroupSharedRecursive/groupShareTree in osowner plus a new Group option, with unix/windows build-constrained implementations and tests.
• Updated installFromSteam to validate SteamCMDPath, group-share it for the su_user, and run steamcmd with WorkDir = SteamCMDPath, FallbackWorkDir = server.WorkDir, and HOME pointing at the steamcmd directory.
• Extended the unix executor to propagate supplementary groups onto syscall.Credential and to upsert env entries (so a caller-supplied HOME is not duplicated/shadowed), plus README/config docs for steam_config.group.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
README.md	Documents new steamcmd_path / steam_config.group settings and the setgid/group-sharing behavior.
internal/app/config/config.go	Adds Group field to SteamConfig for the shared OS group.
internal/app/osowner/owner.go	New Group option, resolveGroupID, and ApplyGroupSharedRecursive helper.
internal/app/osowner/owner_unix.go	Unix implementation of groupShareTree (setgid + group bits, chown group only).
internal/app/osowner/owner_windows.go	Windows no-op stub for groupShareTree.
internal/app/osowner/owner_test.go	Tests for noop and root-mode behavior of ApplyGroupSharedRecursive.
internal/app/game_server_commands/install_server.go	Validates SteamCMD path, applies group-share, sets WorkDir/FallbackWorkDir/HOME for steamcmd.
internal/app/game_server_commands/install_server_test.go	Updates steam install/update tests to use SteamCMDPath and assert executor options.
internal/app/components/executor_unix.go	Sets supplementary groups on the credential and upserts caller-supplied env (notably HOME).

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[coveralls]

Coverage Report for CI Build 25963657544

Coverage decreased (-0.2%) to 36.215%

Details

• Coverage decreased (-0.2%) from the base build.
• Patch coverage: 105 uncovered changes across 4 files (20 of 125 lines covered, 16.0%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
internal/app/components/executor_unix.go	40	0	0.0%
internal/app/osowner/owner_unix.go	28	0	0.0%
internal/app/osowner/owner.go	37	10	27.03%
internal/app/game_server_commands/install_server.go	20	10	50.0%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	12782
Covered Lines:	4629
Line Coverage:	36.21%
Coverage Strength:	23645.54 hits per line

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💛 - Coveralls