macOS CI: 7 vm-temp mount/path integration tests fail

[mudcube]

Context

Once CI actually started running the test suite (the working-directory: rust fix in #63), the macos-latest leg surfaced pre-existing failures unrelated to that PR's changes. The macOS CI leg is currently advisory (continue-on-error) so it doesn't block merges; this issue tracks fixing it for real.

Symptom

7 of 8 tests in rust/vm-temp/tests/integration_tests.rs fail on macOS (they pass on Linux):

• test_concurrent_state_operations
• test_mount_filesystem_integration
• test_mount_path_edge_cases
• test_mount_permission_scenarios
• test_mount_source_validation_edge_cases
• test_mount_workflow_integration
• test_state_file_atomic_operations

(test_mount_*-style names + state-file ops.)

Likely cause

macOS path/filesystem semantics differ from Linux — e.g. /var → /private/var symlink canonicalization, temp-dir layout, and the permission model. These are almost certainly assertions that hard-code Linux path assumptions.

Repro

cargo test -p vm-temp --test integration_tests

on macOS.

Evidence

Failing run (commit d67c747): https://github.com/goobits/vm/actions/runs/28057405127/job/83063072667

Done when

macOS CI passes these tests and the continue-on-error advisory flag can be removed from the macOS matrix leg in .github/workflows/ci.yml.