style(e2e): drop unused spawnSync import and prefer Record

Static analysis rejected an unused spawnSync import in the reap fixture
and an index signature on spawnSignalFixture extraEnv.

Author: TheGreatAxios

e2e/signal-helpers.ts

@@ -65,9 +65,10 @@ export interface SpawnSignalFixtureOptions {
    */
   readonly extraEnv?:
     | Record<string, string>
-    | ((dirs: { readonly cwd: string; readonly home: string }) => {
-        readonly [key: string]: string;
-      });
+    | ((dirs: { readonly cwd: string; readonly home: string }) => Record<
+        string,
+        string
+      >);
 }
 
 /**

fixtures/exec-shutdown-reap/simulate-reap.ts

@@ -2,7 +2,6 @@
 // sleep through the real shell-guard plugin, registers exec dispose as the
 // process dispose host, then takes the requested exit path so the parent can
 // assert the child was reaped.
-import { spawnSync } from "node:child_process";
 import { writeFileSync } from "node:fs";
 import type { ToolCall, ToolResult } from "@intx/types/runtime";