Add macOS workspace CLI support

[yzim]

Summary

This PR adds agentvfs workspace ... support on macOS and wires the macOS build to include the shared workspace CLI implementation.

Changes

• dispatch agentvfs workspace from the macOS entrypoint
• link src/cas/workspace_cli.cpp into the macOS agentvfs target
• make shared workspace lifecycle helpers work on macOS
• allow the macOS daemon parser to accept both --sock and --control-sock
• keep shared workspace spawning aligned with the Linux-style --control-sock flag
• add a macOS workspace CLI system test under tests/system/macos/test_workspace_cli.sh
• run the new macOS workspace CLI test in CI alongside the existing direct-mount macOS test

Notes

• Linux/shared workspace code uses --control-sock
• existing direct macOS usage/help still shows --sock but --control-sock is added to align with Linux code.
• this PR keeps macOS compatible with both forms so workspace flows work without changing the shared caller
• the macOS workspace test is placed under the dedicated tests/system/macos/ directory; broader test-directory refactoring is split into a separate PR

[Zhihaoi]

LGTM. Thanks.