test(code-runtime-python): update CPU-timeout assertions to the reworded message

The SIGXCPU timeout message changed from "CPU budget (Ns) exhausted" to name the
configured value as a ceiling; two existing timeout tests asserted the old text.
Assert "CPU time exhausted" to match.

packages/code-runtime/code-runtime-python/tests/runtime.spec.ts

@@ -1618,7 +1618,7 @@ describe('PythonCodeRuntime — budgets, termination, disposal', () => {
       bindings: [],
     })
     expect(result.error?.kind).toBe('timeout')
-    expect(result.error?.message).toContain('CPU budget')
+    expect(result.error?.message).toContain('CPU time exhausted')
   }, 8000)
 
   it('keeps an early self-inflicted SIGKILL a worker-exit, not a CPU timeout', async () => {
@@ -1822,7 +1822,7 @@ describe('PythonCodeRuntime — budgets, termination, disposal', () => {
       bindings: [],
     })
     expect(result.error?.kind).toBe('timeout')
-    expect(result.error?.message).toContain('CPU budget')
+    expect(result.error?.message).toContain('CPU time exhausted')
     expect(result.value).toBeUndefined()
   }, 15_000)