fix(installer): install release formula from Homebrew tap

[drew]

Summary

Fix the macOS install-dev.sh Homebrew path by staging the downloaded release formula in the nvidia/openshell tap before installing it. This avoids current Homebrew rejecting temp openshell.rb paths while preserving the release formula install flow for either the default dev release or a tagged release selected with OPENSHELL_VERSION.

The change also makes the formula postinstall idempotent so reinstalls can refresh the Hypervisor entitlement plist and re-run codesign.

Related Issue

None.

Changes

• Stage the downloaded release formula into the nvidia/openshell Homebrew tap before install or reinstall.
• Install and restart services by fully qualified formula name.
• Patch older downloaded formulas locally from entitlements.write to entitlements.atomic_write before staging.
• Update the generated Homebrew formula to use atomic_write for the entitlement plist going forward.
• Document the tap behavior in the VM driver README.

Testing

• mise run pre-commit passes
• Unit tests added/updated
• E2E tests added/updated (if applicable)
• sh -n install-dev.sh
• shellcheck install-dev.sh
• uv run pytest python/openshell/release_formula_test.py
• git diff --check
• sh ./install-dev.sh verified Homebrew reinstall from nvidia/openshell/openshell, postinstall codesign, and qualified service restart

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (if applicable)