- Receiver: auto-fill and join on Retrieve tab when input empty, not in room, no URL roomId, and cachedId exists (ClipboardApp + roomIdCache)
- Sender: “Use cached ID” now immediately joins the room (add onUseCached + disabled to CachedIdActionButton; wire in SendTabPanel)
- UI: add ThemeToggle and integrate into Header (desktop and mobile)
- Styles: replace hardcoded white with design tokens in Retrieve panel (bg-card/text-card-foreground) for dark mode
- Docs: update AI playbook flows and code-map