[GOV.32] Remove the ContentSandbox macOS launch-profile code and keep the typed fail-closed refusal

[deku2026]

Claim: GOV.32 epoch 1 (w-deku-20261008-gov-32)

Task record: governance lane, task-gov-32. Authority: P2-023, under which macOS is outside the delivery scope. The task was added by the planning repair Design #341 / Plan #457.

What this changes

• Deletes the declarative macOS entitlements input src/DesktopHelpers/ArcForges.ContentSandbox/macos/ArcForges.ContentSandbox.entitlements and its eng/provenance/files.json row.
• Makes ProfileEnforcement.ThisPlatform a nullable ContentSandboxProfileKind? that is null on every OS other than Windows and Linux. HelperEntry compares the frame profile with it unchanged, so every launch frame there, including one carrying the reserved MacOsAppSandboxXpc, exits with the isolation-unavailable code (70) before any resource or parser is reached. The Windows and Linux branches are unchanged.
• Rewrites Tests/MacProfileTests.cs to cover refusal only. It checks that:
  • the broker refuses a macOS launch;
  • the reserved value stays wire-stable at 3;
  • the Windows (1) and Linux (2) kinds are unchanged;
  • a helper given a MacOsAppSandboxXpc frame exits 70.
• Tests/ContractFacadeTests.cs: the refusal check covers every non-Windows, non-Linux OS.
• The README macOS lines and the doc comments of the reserved enum value now state that macOS is not supported. The value itself is unchanged.

No change to Windows or Linux containment. ContentSandboxLauncher.cs (the macOS refusal) and HelperEntry.cs are not edited.

Validation (independent reviewer runs)

• Windows and WSL2 Debian, SDK 10.0.400, Linux-native clone: locked restore, build with warnings as errors, and the ContentSandbox tests: 110 total, 101 passed, 0 failed, 9 opt-in OS isolation tests skipped.
• Python gates: design, dependency, licence boundary (--evaluate-managed and --evaluate-ide), reference baselines, runtime ownership, architecture naming evidence, reconciliation, provenance, native provenance and stage-integration verify all pass, as do the eng, tests/tooling and stage_integration unit suites.
• eng/packaging unit suite: needs pack output first, which hosted package-validation produces.

🤖 Generated with Claude Code

[deku2026]

Reviewed 45343a4 for [GOV.32] (ContentSandbox macOS profile code removal): approved

Independent reviewer session w-deku-20261008-rev-gov-32, which authored none of this. Posted by the coordinator under the 2026-10-08 publication protocol.

Round 1, by inspection:

• write scope: the 9 record files only;
• Windows and Linux containment unchanged;
• the nullable ThisPlatform refuses every frame off Windows and Linux;
• the wire value stays 3;
• no residual App-Sandbox/XPC/entitlements code outside the reserved value, the launcher refusal and the docs and tests.

Validation was not yet run in that round.

Round 2, approved with full validation under SDK 10.0.400:

• Windows: tests 110 total, 101 passed, 9 opt-in OS isolation tests skipped.
• WSL2 Debian on a Linux-native clone: the same totals.
• All Python gates and unit suites pass. The eng/packaging suite needs pack output, which hosted CI produces.

Non-blocking: ContentSandboxLauncher.ProbeProfile() on macOS still reports the reserved value as an unavailable profile, with a reason text about the removed bundle/XPC handoff. The launcher is outside this write scope; the refusal itself is correct.