Add the CONTROLLER-mode device picker. New QconnectDevice struct + devices /
active-renderer-id / set-active on the QconnectDevState global (re-exported via
app.slint so include_modules! generates the type). The connect flyout replaces
the "No devices found" placeholder with a plain-row list (ADR-008: no pills)
when session renderers exist: each row taps to set-active and closes the menu;
the local device renders as "Play here" to pull playback back to QBZ. A
"Playing on: {name}" header shows while a peer is active.
The event sink rebuilds the device list and pushes the cast-aware now-playing
state (is-remote / cast-target / volume-locked) from session topology after
every event, replacing the prior TODO. main.rs wires on_set_active to the new
SlintQconnectService::set_active_renderer (over send_set_active_renderer).
Wired but unverified (blind build, no phone+speaker); device round-trips need a
smoke test. Slice 4 (peer-state reflection in the poll loop) deferred.
cc
vicrodh
0d7ac7930d