carry of #27944: Cloud pause/resume actions
Carry of #27944 (https://github.com/manaflow-ai/cmux/pull/27944), preserving its purpose: “cmux NEXT Cloud: offer Pause or Resume Machine by the machine's state.”
This carry preserves the original commits and merges feat-cmux-next. Resume disappears from the machine menu only while its daemon connection is attached and connected. A cached API status can lag server idle-pause or app-link resume, so disconnected machines keep both actions and explicit Pause/Resume commands remain idempotent.
Regression coverage exercises stale running and paused records, a live daemon behind a stale paused record, and a kept handshake without a connection. Risk: uncertain machines show both commands; the server remains authoritative.
Capture validation: the Cloud capture route refuses whole-host capture, and the non-Cloud tour has no Cloud session. Base and head therefore render the same menu, so those captures cannot demonstrate this behavior.
No capture: the available capture routes cannot reproduce the relevant Cloud session states described above.
Fleet validation at 4deec0a1f77ba6c978bee0747b94e502218df20f: CloudPauseResumeAvailabilityTests passed 6/6. These tests provide the evidence for Pause/Resume availability across live connections and stale machine records.
Agent session: agent session