websockets>=14 defaults to proxy=True and resolves proxies via
urllib.request.getproxies(), which reads the macOS/Windows system
proxy config even with no *_proxy env vars set. Local CDP endpoints
(ws://127.0.0.1:<port>/devtools/...) were therefore dialed through
the system proxy and the handshake failed with "did not receive a
valid HTTP response" (#110565).
Append 127.0.0.1/localhost/::1 to NO_PROXY/no_proxy (both casings)
in _build_browser_env so every browser subprocess (Browser Use CLI,
agent-browser, Chromium, Lightpanda) bypasses proxies for loopback.
Operator-provided NO_PROXY entries are preserved.
Fixes#110565
00a68a8768