test(code-runtime-python): pin send_done against rebinding write_encoded and _encode_json_plain

The rebinds-every-name fixture previously only rebound ProtocolChannel.send_sync,
which a bound method object ignores and the shipped send_done no longer calls —
so it did not actually guard the call-time-lookup shape. Rebind write_encoded
and _encode_json_plain too (the names send_done would resolve late if it looked
them up at call time) and state that in the settlement note's Testing section
(en + zh), re-recording the pairing.

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

@@ -1412,7 +1412,12 @@ describe('PythonCodeRuntime — programs and bindings', () => {
         '__main__._model_traceback = boom',
         '__main__._UNRENDERABLE_DIAGNOSTIC = boom',
         '__main__._LogStream.flush_line = boom',
+        // `send_done` writes via LOCALLY-BOUND `_encode_json_plain` +
+        // `ProtocolChannel.write_encoded`; rebinding these at call time must not
+        // redirect the done frame (a late lookup would be `boom` -> worker-exit).
         '__main__.ProtocolChannel.send_sync = boom',
+        '__main__.ProtocolChannel.write_encoded = boom',
+        '__main__._encode_json_plain = boom',
         'raise ValueError("real failure")',
       ].join('\n'),
       bindings: [],