test: make unsafe test coercion explicit

Move test coercion out of a hidden global and require each test to import the helper so review tools and runtime scripts can see the unsafe boundary.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/task-resume-info/index.test.ts

@@ -2,6 +2,7 @@
 
 import { describe, it, expect } from "bun:test"
 import { createTaskResumeInfoHook } from "./index"
+import { unsafeTestValue } from "../../../test-support/unsafe-test-value"
 
 describe("createTaskResumeInfoHook", () => {
   const hook = createTaskResumeInfoHook()
@@ -19,7 +20,7 @@ describe("createTaskResumeInfoHook", () => {
         const input = createInput("task")
         const output = {
           title: "delegate_task",
-          output: testCoerce<string>(undefined),
+          output: unsafeTestValue<string>(undefined),
           metadata: {},
         }