fix: use empty string to clear away status

The Twist API accepts an empty string (not null) to clear the
away_mode field.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: lmjabreu

src/__tests__/away.test.ts

@@ -145,13 +145,13 @@ describe('away', () => {
     })
 
     describe('clear', () => {
-        it('calls users.update with null awayMode', async () => {
+        it('calls users.update with empty string awayMode to clear', async () => {
             const logSpy = vi.spyOn(console, 'log').mockImplementation(() => {})
             const program = createProgram()
 
             await program.parseAsync(['node', 'tw', 'away', 'clear'])
 
-            expect(apiMocks.updateUser).toHaveBeenCalledWith({ awayMode: null })
+            expect(apiMocks.updateUser).toHaveBeenCalledWith({ awayMode: '' })
             expect(logSpy).toHaveBeenCalledWith('Away status cleared.')
             logSpy.mockRestore()
         })

src/commands/away.ts

@@ -92,7 +92,7 @@ async function clearAway(options: MutationOptions & ViewOptions): Promise<void>
     }
 
     const client = await getTwistClient()
-    const user = await client.users.update({ awayMode: null as never })
+    const user = await client.users.update({ awayMode: '' as never })
 
     if (options.json) {
         console.log(formatJson(user, 'user', options.full))