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/cli/install.test.ts

@@ -5,6 +5,7 @@ import { join } from "node:path"
 import { install } from "./install"
 import * as configManager from "./config-manager"
 import type { InstallArgs } from "./types"
+import { unsafeTestValue } from "../../test-support/unsafe-test-value"
 
 // Mock console methods to capture output
 const mockConsoleLog = mock(() => {})
@@ -57,7 +58,7 @@ describe("install CLI - binary check behavior", () => {
     getOpenCodeVersionSpy = spyOn(configManager, "getOpenCodeVersion").mockResolvedValue(null)
 
     // given mock npm fetch
-    globalThis.fetch = testCoerce<typeof fetch>(mock(() =>
+    globalThis.fetch = unsafeTestValue<typeof fetch>(mock(() =>
       Promise.resolve({
         ok: true,
         json: () => Promise.resolve({ latest: "3.0.0" }),
@@ -92,7 +93,7 @@ describe("install CLI - binary check behavior", () => {
     getOpenCodeVersionSpy = spyOn(configManager, "getOpenCodeVersion").mockResolvedValue(null)
 
     // given mock npm fetch
-    globalThis.fetch = testCoerce<typeof fetch>(mock(() =>
+    globalThis.fetch = unsafeTestValue<typeof fetch>(mock(() =>
       Promise.resolve({
         ok: true,
         json: () => Promise.resolve({ latest: "3.0.0" }),
@@ -131,7 +132,7 @@ describe("install CLI - binary check behavior", () => {
     getOpenCodeVersionSpy = spyOn(configManager, "getOpenCodeVersion").mockResolvedValue("1.4.0")
 
     // given mock npm fetch
-    globalThis.fetch = testCoerce<typeof fetch>(mock(() =>
+    globalThis.fetch = unsafeTestValue<typeof fetch>(mock(() =>
       Promise.resolve({
         ok: true,
         json: () => Promise.resolve({ latest: "3.0.0" }),