Tauri creates one app session per spec file; multiple files caused
invalid session id on subsequent specs. WebDriver clicks on Svelte 5
components inside scrollable panels dont trigger onclick handlers
via WebKit2GTK/tauri-driver - use browser.execute() JS clicks.
Also removed tauri-plugin-log (redundant with telemetry::init()).
Create Cargo workspace at v2/ level with members: src-tauri,
bterminal-core, bterminal-relay. Extract PtyManager and SidecarManager
into shared bterminal-core crate with EventSink trait for abstracting
event emission. TauriEventSink wraps AppHandle. src-tauri pty.rs and
sidecar.rs become thin re-exports. Move Cargo.lock to workspace root.
Add v2/target/ to .gitignore.