Prevent the desktop app from sleeping during active generation or live sessions

[KSemenenko]

Problem

When dotPilot is actively generating output or running a live session, the desktop app should stop the computer from sleeping so long-running work is not interrupted.

Scope

• Track OS-level sleep prevention while a session is actively generating or otherwise marked live
• Define the exact trigger states that acquire the sleep-prevention lock
• Define the exact release states that remove the lock when work is done, paused, failed, or otherwise no longer active
• Cover macOS, Windows, and Linux desktop behavior
• Keep the operator aware that the app is holding a sleep-prevention assertion

Out of scope

• Browser or web-hosted behavior
• Provider-specific keepalive hacks
• Preventing sleep when no session is active
• Hiding the sleep-prevention state from the operator

Implementation notes

• Use native platform power-management APIs from the desktop host instead of fake background activity
• Tie the behavior to explicit session lifecycle and generation state, not to vague heuristics
• Acquire the assertion only while real foreground or background session work is active
• Release it immediately when the session is completed, canceled, paused, failed, or otherwise no longer live
• Make the state inspectable from the product so operators understand why the machine is being kept awake

Definition of Done

• The issue defines when dotPilot must block system sleep and when it must release that block
• The issue covers the operator-visible status for the sleep-prevention state
• Later implementation can proceed without re-deciding the product behavior per OS

Verification

• Review the issue against the session, fleet, and runtime-lifecycle backlog
• The issue keeps sleep prevention explicit and bounded to active work only

Dependencies

• Parent epic: [Epic] Build the agent catalog and fleet-management experience #16
• Related epic: [Epic] Add the embedded agent runtime host to the Uno desktop app #12