fix(windows): restore MXC qualification and cold-start readiness

[prekshivyas]

Summary

• restore the Windows MXC qualification/build gates against the current OpenShell APIs
• preserve cmd.exe command-tail quoting for paths and redirection
• stage libz3.dll with Windows release artifacts
• keep the supervisor relay probing for the full five-minute cold-start budget advertised by the MXC driver

Why

On a cold Windows ARM64 host, Defender first-touch scanning can delay OpenClaw readiness beyond three minutes. The MXC driver allows 310 seconds, but the relay stopped probing after 180 seconds, causing a false startup failure even when OpenClaw became ready within the advertised window.

Validation

• cargo test -p openshell-supervisor-relay: 14 passed
• Windows ARM64 native release build completed successfully
• focused NemoClaw attachment and E2E support tests: 135 passed, 1 intentional skip
• authoritative Windows ARM64 live qualification: two consecutive create/start/policy/forward/chat/delete cycles passed in 34m59s
• both qualification receipts passed all 14 checks with no emergency process termination

The OpenClaw archive/staging optimization used by qualification is maintained in NemoClaw and is not included in this OpenShell PR.