bug: recv_all can block indefinitely: it waits for channel.recv_ready() with no timeout, which can hang the entire test suite on failures/flaky timing. Add a maximum wait duration (or Paramiko channel timeouts) and fail with a clear assertion if no data arrives.

[ncouture]

recv_all can block indefinitely: it waits for channel.recv_ready() with no timeout, which can hang the entire test suite on failures/flaky timing. Add a maximum wait duration (or Paramiko channel timeouts) and fail with a clear assertion if no data arrives.

Originally posted by @Copilot in #34 (comment)