[Brekit]

Problem and resulting behavior

Native macOS launches were limited by an AppID-specific save-directory check, a bundle-only platform adapter, and two independent choices of Steam launch option. Games whose Steam entry points to a script or binary could fail before their actual executable started. This change derives one launch plan from Steam metadata and the installed files, preserves the numeric launch-option ID, and handles bundles, Mach-O binaries and supported sh/bash launch scripts without per-game AppID rules.

Steam Auto-Cloud paths and platform overrides are carried through the PICS catalog and resolved to specific game-associated directories. Legacy cached entries refresh their app metadata before native launch. SDK discovery is optional and bounded; a missing or ambiguous diagnostic SDK no longer blocks a valid target. Script launches keep their original arguments, working directory and Steam context; a dedicated process group and private launch markers allow the final game process to be tracked after its script exits.

Dota 2 reached a Source 2 single-instance warning because the worker could not create its normal temporary lock. Native workers now permit only numeric source_engine_*.lock files in the POSIX temporary root. Existing lock files are not removed and kernel lock exclusion remains intact. Dota 2 now reaches its main menu through SkinOS's Play button, using its existing macOS installation and no original Steam GUI.

Validation

• Full Rust workspace tests and strict workspace Clippy passed. The combined review candidate passed the full Rust workspace, strict Clippy, all 76 Swift tests and the five bootstrap-boundary tests.
• Parser/selector regressions cover sparse launch IDs, text/binary UFS parity, metadata refresh and legacy caches.
• Native fixtures cover bundles, binaries, script arguments and cwd, lock-descriptor closure, unsafe targets, SDK scan limits and optional probing.
• A real macOS fixture verifies the correct background-child PID after the script has exited and been reaped.
• A real sandbox fixture verifies that Source 2-style lock creation succeeds, a second exclusive lock is rejected, lookalike temporary paths and a private canary remain inaccessible.
• Development build 0.1.5 (build 6) was installed locally. Dota was launched through the app; the user confirmed the normal main menu. The latest log has no Source 2 lock error and shows Steamworks and the graphics backend initializing. No original Steam GUI process was observed; an already-running background IPC broker was left untouched.

Review fixes

• Accept Steam Auto-Cloud GameInstall / . for the verified installation while retaining restrictions on whole user-data containers.
• Refresh native launch and save metadata for every launch, including already-known cached games after an update.
• Share the protocol launch-entry conversion and document the vendored API changes.
• Replace the one-second background-process fixture with an owned native helper and explicit readiness/release handshakes. A forced scheduling delay reproduced the former failure; the revised fixture passes it.

Review notes

PR #1 is merged. This PR targets main and contains the native-launch work and its review fixes. Version 0.1.5 / build 6 combines both changes for the signed release.

This does not claim that every Steam game is compatible. Unsupported script interpreters and unverified save-root mappings still produce explicit errors. Cloud metadata is used to determine paths; Cloud synchronization itself is outside this change. Multiplayer and physical-controller behavior were not tested here. SDK diagnostics can be skipped for unsupported architectures; runtime ownership checks remain mandatory.

• The diff contains no credentials, personal account data, game files or generated app bundles.
• Third-party source retains its license and upstream attribution.
• Documentation and regression coverage reflect the behavior changed, where applicable.