docs(agents): Keep the Python bindings for outside users
The repository drove pixelflux and pcmflux through their Python bindings
in 13 places beyond the bindings' own tests and examples: the V4L2
interposer's test server, a screenshot repro script, seven integration
suites and four e2e suites, for a stand-in camera, a clipboard write, or
a question about the server's capabilities.
AGENTS.md now says the bindings serve outside users: nothing here drives
the libraries through them but their own tests and examples, and tools
and tests reach the libraries through the Rust API, the server, or its
commands. The 13 uses move with the test port.