test(cli): remove unsafe test assertions

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

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

src/cli/install.test.ts

@@ -57,12 +57,12 @@ describe("install CLI - binary check behavior", () => {
     getOpenCodeVersionSpy = spyOn(configManager, "getOpenCodeVersion").mockResolvedValue(null)
 
     // given mock npm fetch
-    globalThis.fetch = mock(() =>
+    globalThis.fetch = testCoerce<typeof fetch>(mock(() =>
       Promise.resolve({
         ok: true,
         json: () => Promise.resolve({ latest: "3.0.0" }),
       } as Response)
-    ) as unknown as typeof fetch
+    ))
 
     const args: InstallArgs = {
       tui: false,
@@ -92,12 +92,12 @@ describe("install CLI - binary check behavior", () => {
     getOpenCodeVersionSpy = spyOn(configManager, "getOpenCodeVersion").mockResolvedValue(null)
 
     // given mock npm fetch
-    globalThis.fetch = mock(() =>
+    globalThis.fetch = testCoerce<typeof fetch>(mock(() =>
       Promise.resolve({
         ok: true,
         json: () => Promise.resolve({ latest: "3.0.0" }),
       } as Response)
-    ) as unknown as typeof fetch
+    ))
 
     const args: InstallArgs = {
       tui: false,
@@ -131,12 +131,12 @@ describe("install CLI - binary check behavior", () => {
     getOpenCodeVersionSpy = spyOn(configManager, "getOpenCodeVersion").mockResolvedValue("1.4.0")
 
     // given mock npm fetch
-    globalThis.fetch = mock(() =>
+    globalThis.fetch = testCoerce<typeof fetch>(mock(() =>
       Promise.resolve({
         ok: true,
         json: () => Promise.resolve({ latest: "3.0.0" }),
       } as Response)
-    ) as unknown as typeof fetch
+    ))
 
     const args: InstallArgs = {
       tui: false,