refactor(core)!: rework agent run lifecycle and status semantics

BREAKING CHANGE: stop() is now async and resolves after the run fully
settles; status decouples from task outcome (new 'stopped' state, LLM
self-reported failure now ends as 'completed'). Lifecycle hooks re-throw
instead of being folded into the result; agent errors go to history.
Adds agent.lastResult.

packages/extension/src/components/misc.tsx

@@ -14,6 +14,7 @@ export function StatusDot({ status }: { status: AgentStatus }) {
 		running: 'bg-blue-500',
 		completed: 'bg-green-500',
 		error: 'bg-destructive',
+		stopped: 'bg-muted-foreground',
 	}[status]
 
 	const label = {
@@ -21,6 +22,7 @@ export function StatusDot({ status }: { status: AgentStatus }) {
 		running: 'Running',
 		completed: 'Done',
 		error: 'Error',
+		stopped: 'Stopped',
 	}[status]
 
 	return (