E2E harness fixes to get all three modes (demo/cloud/local) passing:
- conftest.py: use ctx.add_cookies() for cloud auth instead of
ctx.route() or set_extra_http_headers(). Playwright's route() only
intercepts HTTP; set_extra_http_headers() explicitly excludes
WebSocket handshakes. Streamlit reads st.context.headers from the
WebSocket upgrade, so cookies are the only vehicle that reaches it
without a reverse proxy.
- cloud_session.py: fall back to Cookie header when X-CF-Session is
absent — supports direct access (E2E tests, dev without Caddy).
In production Caddy sets X-CF-Session; in tests the cf_session cookie
is set on the browser context and arrives in the Cookie header.
- modes/cloud.py: add /peregrine base URL path (STREAMLIT_SERVER_BASE_URL_PATH=peregrine)
- modes/local.py: correct port from 8502 → 8501 and add /peregrine path
All three modes now pass smoke + interaction tests clean.
