test: add typed test coercion helper

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

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

src/testing/test-coerce-global.d.ts

@@ -0,0 +1,5 @@
+declare global {
+	function testCoerce<TValue>(value: TValue): TValue
+}
+
+export {}

test-setup.ts

@@ -11,6 +11,8 @@ const { restoreModuleMocks } = installModuleMockLifecycle(mock)
 let environmentSnapshot: NodeJS.ProcessEnv = { ...process.env }
 let workingDirectorySnapshot = process.cwd()
 
+globalThis.testCoerce = <TValue>(value: TValue): TValue => value
+
 function cleanupOmoCacheDir(cacheDir: string): void {
   rmSync(cacheDir, { recursive: true, force: true })
 }