feat(FN-1757): clear residual lint debt in engine package

- Remove unused imports across 25 files in engine package
- Remove unused variable declarations in ipc-worker.ts, child-process-runtime.ts, and mission-autopilot.ts
- Clean up unnecessary imports in agent-instructions.ts, agent-tools.ts, cron-runner.ts, executor.ts, and other modules
- Minor cleanup in notifier.ts, peer-exchange-service.ts, pi.ts, plugin-runner.ts, and other files
- Improves code quality and reduces potential confusion from unused code

packages/engine/src/hybrid-executor.ts

@@ -8,7 +8,7 @@ import type {
   RuntimeStatus,
   GlobalMetrics,
 } from "./project-runtime.js";
-import type { ProjectManagerEvents } from "./project-manager.js";
+
 import { hybridExecutorLog } from "./logger.js";
 
 /**
@@ -261,7 +261,7 @@ export class HybridExecutor extends EventEmitter<HybridExecutorEvents> {
       throw new Error(`Runtime not found for project ${projectId}`);
     }
 
-    const currentStatus = existingRuntime.getStatus();
+    const _currentStatus = existingRuntime.getStatus();
     const currentMode =
       existingRuntime instanceof
       (await import("./runtimes/child-process-runtime.js")).ChildProcessRuntime