fix(FN-4606): stabilize resolver callsites and test expectations

Ref: Runfusion/Fusion#321
Fusion-Task-Id: FN-4606
Fusion-Task-Lineage: 94b23f37-944e-4bcd-bfa1-67d0a8c0a267

packages/engine/src/step-session-executor.ts

@@ -15,7 +15,6 @@ import { promisify } from "node:util";
 
 const execAsync = promisify(exec);
 import { existsSync } from "node:fs";
-import { join } from "node:path";
 import type { AgentSession } from "@mariozechner/pi-coding-agent";
 import type { AgentStore, MessageStore, PermanentAgentGatingContext, TaskDetail, Settings, TaskStore } from "@fusion/core";
 import { resolvePersistAgentThinkingLog } from "@fusion/core";