Navigation fixes:
- The bottom "Explore" sheet no longer blocks the top bar: closed state is
visibility:hidden (out of hit-testing), so the top identity buttons and page
content always receive taps (fixes "top buttons don't work").
- Top bar is now identity only (logo, avatar). The Personal/Community filter
moved into the Explore sheet, next to the hive, as a segmented control.
New module "Karvan" (self-contained; inspired by karvan-protocol ephemeral rooms):
- Ephemeral/temporary chat rooms held only in RAM, self-destructing on idle
(30 min) / absolute (2 h) TTL — nothing is written to disk.
- Server relay chat (RAM + polling) as the reliable path, plus a WebRTC
data-channel layer (perfect negotiation, HTTP signaling mailbox) for instant
P2P delivery; degrades to the relay if WebRTC is unavailable. Data-channel
only (no camera/mic) so no wrapper permission changes are needed.
- Files: models/karvan_model.js, views/karvan_view.js, client/public/js/karvan.js;
routes /karvan* + karvanMod config + nav entry (network) + karvanTitle i18n (11 langs).
Additive and gated by OASIS_MOBILE / karvanMod; Linux and the UX_OASIS branch untouched.
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