Remove the legacy operator UI streaming page

The operator UI that streamed OpenHTF tests from the Python client to a dashboard page has been replaced by the CLI, which runs the same unmodified scripts with a live operator UI on any browser.

• Removed the legacy streaming page and the server endpoint older Python clients called to reach it; those clients now stop retrying at once instead of logging a warning every second.
• Removed the "streaming was removed" warning the Python client logged when a script passed stream=True; the argument is still accepted and ignored.
• Planned: the TofuPilot OpenHTF context manager, deprecated with a warning since August 11, 2026, will be removed in a future release. Run your tests with tofupilot run instead, or register the upload() callback if you manage your own pipeline.