* fix(mobile): restart the streamed browser pane on every return to the app
The browser pane stops its screencast when the app leaves the foreground and
starts a new one when it comes back, keyed on an `appActive` boolean. When the
leave and the return are handled in one React render (the JS thread was held
across the whole trip, as a suspended or frozen app is), React applies
false-then-true as no change, so the stream effect never re-runs: the old
subscription is kept and no new one starts. If the desktop ended that
subscription while the phone was away (it evicts a viewer whose socket
refuses 90 frames in a row), the pane shows the last frame it had
indefinitely, with no error and nothing that would restart it.
The pane now keeps `foregroundVisit`: null while the app is away and a new id
on each return. A batched leave-and-return still moves it to a new value, so
every return starts a fresh stream, and the host's start snapshot repaints the
pane.
* refactor(mobile): drop a busy reset both stream-effect branches overwrite
Jinwoo Hong
c4e58fac56