feat(FN-1401): integrate PluginRunner into runtime lifecycle

- Integrate PluginRunner into InProcessRuntime for plugin lifecycle management
- Wire plugin:created, plugin:updated, plugin:deleted events through runtime event bus
- Add plugin tools to StepSessionExecutor so plugins can provide tools during step execution
- Fix PluginRunner to pass PluginContext to task lifecycle hooks (onTaskCreated, onTaskUpdated, etc.)
- Add PluginRunner tests covering init/shutdown, timeout isolation, and sync event behavior
- Add InProcessRuntime tests verifying plugin integration
- Update memory documentation with plugin runner lifecycle wiring

packages/engine/src/executor.ts

@@ -1003,6 +1003,7 @@ export class TaskExecutor {
           settings,
           semaphore: this.options.semaphore,
           stuckTaskDetector: this.options.stuckTaskDetector,
+          pluginRunner: this.options.pluginRunner,
           onStepStart: (stepIndex) => {
             this.options.stuckTaskDetector?.recordProgress(task.id);
             try {