M6 epic: Guest lifecycle and task operations

[Andreas-Froyland]

Tracking issue. Dependency and status checklists only — implementation stays in narrow linked issues.

Outcome

Bounded start/stop/shutdown/reboot operations run as durable, audited Fleet operations with real UPID task progress.

Supersedes

Replaces the "VM boot/stop" and lifecycle: power-state portions of #3. The legacy UPID polling and certificate-fingerprint tests are preserved as requirements.

Depends on

• M6 VM/LXC associations and guest data
• FM-108/FM-109 — durable operations and worker (M1)

Scope checklist

• Start, stop, shutdown, reboot mapped to durable operations
• UPID task polling with progress, cancellation, and deadlines
• Deterministic timeout behavior (no wall-clock-sensitive polling; see the legacy waitForTask flake noted in docs/PLAN.md)
• Partial-node failure and privilege failure surfaced per resource

Constrained by

• docs/PLAN.md — M6; ADR-0008
• Mutating APIs return operation handles

Non-goals

• Destructive operations (template/clone/snapshot epic)
• Guest OS provisioning; that is Ansible/Nix/profile work, not Fleet's