fix(agent): preserve Windows supervisor ownership

[jmagar]

Summary

• restart updated Windows agents through the existing CortexHeartbeatAgent scheduled task
• wait until the prior task instance is restartable
• retain direct ProcessStartInfo launch only for unsupervised installs
• use the same supervisor-aware start path for rollback fallback

Verification

• Windows handoff script regression test passes
• Windows cross-target cargo check passes
• pre-push clippy/version/module gates pass
• live v3.13 investigation reproduced the orphaned Ready-task state and restored scheduler ownership before this patch