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/ui/src/panel/Panel.ts

@@ -100,10 +100,10 @@ export class Panel {
 	#handleStatusChange(): void {
 		const status = this.#agent.status
 
-		// Map agent status to UI indicator type
-		const indicatorType =
-			status === 'running' ? 'thinking' : status === 'idle' ? 'thinking' : status
-		this.#updateStatusIndicator(indicatorType)
+		// Map agent status to UI indicator. A `completed` run whose result reports
+		// failure shows as error; other statuses map to their own indicator.
+		const failed = status === 'completed' && this.#agent.lastResult?.success === false
+		this.#updateStatusIndicator(failed ? 'error' : status)
 
 		// Morph action button: running = stop (■), not running = close (X)
 		if (status === 'running') {
@@ -121,7 +121,7 @@ export class Panel {
 		}
 
 		// Handle completion
-		if (status === 'completed' || status === 'error') {
+		if (status === 'completed' || status === 'error' || status === 'stopped') {
 			if (!this.#isExpanded) {
 				this.#expand()
 			}
@@ -376,7 +376,7 @@ export class Panel {
 		}
 
 		const status = this.#agent.status
-		const isTaskEnded = status === 'completed' || status === 'error'
+		const isTaskEnded = status === 'completed' || status === 'error' || status === 'stopped'
 
 		// Only show input area after task completion if configured to do so
 		if (isTaskEnded) {
@@ -559,13 +559,23 @@ export class Panel {
 	}
 
 	#updateStatusIndicator(
-		type: 'thinking' | 'executing' | 'executed' | 'retrying' | 'completed' | 'error'
+		type:
+			| 'idle'
+			| 'running'
+			| 'thinking'
+			| 'executing'
+			| 'executed'
+			| 'retrying'
+			| 'completed'
+			| 'error'
+			| 'stopped'
 	): void {
-		// Clear all status classes
+		// `running` animates like thinking; `idle`/`stopped` use the neutral base.
+		const variant = type === 'running' ? 'thinking' : type
 		this.#indicator.className = styles.indicator
-
-		// Add corresponding status class
-		this.#indicator.classList.add(styles[type])
+		if (variant !== 'idle' && variant !== 'stopped') {
+			this.#indicator.classList.add(styles[variant])
+		}
 	}
 
 	#scrollToBottom(): void {

packages/ui/src/panel/types.ts

@@ -22,14 +22,17 @@ export type AgentActivity =
  * This enables decoupling and allows any agent implementation to work with Panel.
  *
  * Events:
- * - 'statuschange': Agent status changed (idle/running/completed/error)
+ * - 'statuschange': Agent status changed
  * - 'historychange': Historical events updated (persisted)
  * - 'activity': Transient activity for immediate UI feedback (thinking/executing/etc)
  * - 'dispose': Agent is being disposed
  */
 export interface PanelAgentAdapter extends EventTarget {
 	/** Current agent status */
-	readonly status: 'idle' | 'running' | 'completed' | 'error'
+	readonly status: 'idle' | 'running' | 'completed' | 'error' | 'stopped'
+
+	/** Result of the most recent run, or `null` before the first run completes */
+	readonly lastResult: { success: boolean } | null
 
 	/** History of agent events */
 	readonly history: readonly {
@@ -71,7 +74,7 @@ export interface PanelAgentAdapter extends EventTarget {
 	execute(task: string): Promise<unknown>
 
 	/** Stop the current task (agent remains reusable) */
-	stop(): void
+	stop(): Promise<void>
 
 	/** Dispose the agent (terminal, cannot be reused) */
 	dispose(): void