test(directory-readme-injector): cover async migration

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

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

src/hooks/directory-readme-injector/injector.test.ts

@@ -133,6 +133,32 @@ describe("processFilePathForReadmeInjection", () => {
     expect(output.output).toContain("# Components README")
   })
 
+  it("returns a promise and finds README.md files from temp fixtures", async () => {
+    // given
+    const sourceDirectory = join(testRoot, "src")
+    const componentsDirectory = join(sourceDirectory, "components")
+    mkdirSync(componentsDirectory, { recursive: true })
+    writeFileSync(join(testRoot, "README.md"), "# Root README")
+    writeFileSync(join(sourceDirectory, "README.md"), "# Src README")
+    writeFileSync(join(componentsDirectory, "README.md"), "# Components README")
+
+    const { findReadmeMdUp } = await import("./finder")
+
+    // when
+    const promise = findReadmeMdUp({
+      startDir: componentsDirectory,
+      rootDir: testRoot,
+    })
+
+    // then
+    expect(promise).toBeInstanceOf(Promise)
+    await expect(promise).resolves.toEqual([
+      join(testRoot, "README.md"),
+      join(sourceDirectory, "README.md"),
+      join(componentsDirectory, "README.md"),
+    ])
+  })
+
   it("does not re-inject already cached directories", async () => {
     // given
     const sourceDirectory = join(testRoot, "src")