Add RenderingCtx enum wrapping SoftwareRenderingContext or
WindowRenderingContext. build_rendering_ctx() checks WEFT_EGL_RENDERING
at startup: if set, attempts WindowRenderingContext::new with the winit
display/window handles and falls back to software on error.
render_frame() dispatches on the variant: software path blits pixels
through softbuffer; EGL path is a no-op (Servo presents directly to
the EGL surface). All WebViewBuilder calls now use RenderingCtx::as_dyn()
to produce Rc<dyn RenderingContext>.
The software path is unchanged. The EGL path is gated behind
WEFT_EGL_RENDERING and only activates with the servo-embed feature.
Task 10 -- App WebView lifecycle.
appd_ws module (servo-embed gated):
Background thread connects to the appd WebSocket on startup.
Sends QUERY_RUNNING to receive initial running sessions.
Translates LAUNCH_ACK -> AppdCmd::Launch and APP_STATE stopped
-> AppdCmd::Stop, then wakes the winit event loop via the
shared EventLoopWaker.
embedder changes:
App struct gains app_rx (mpsc receiver), app_webviews
(HashMap<session_id, WebView>), active_session, and a stored
rendering_context used when creating app WebViews later.
create_app_webview(): resolves weft-app://<app_id>/index.html
to a file URL, creates a dedicated UserContentManager with the
weftIpc bridge injected (includes window.weftSessionId), builds
and registers a new WebView.
about_to_wait() drains app_rx: creates WebViews for Launch
commands, removes and clears active_session for Stop commands.
active_webview() returns the active-session WebView when one
exists, falling back to the system-ui WebView. Rendering,
keyboard, and mouse events all route through active_webview().
Resize propagates to both the system WebView and all app WebViews.
run() creates the mpsc channel and spawns the appd listener
before entering the winit event loop.