Opening the settings pane on mobile set activePaneIdx, but the ?pane= URL-sync
effect snapped it back to the chat pane on the panes change, so the pane never
showed. toggleSettingsPane now returns the new pane id (id generated outside the
updater, strict-mode safe); Session's toggleSettingsAndSync pushes ?pane=<id> on
mobile when opening (and drops it on close) so the sync effect keeps it active —
mirrors the existing addPaneAndSwitch pattern. Desktop unaffected.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
indifferentketchup
21384cce5b