[0.9.1] FORK_IA_UX v2: fix top-bar (visibility sheet) + Karvan module (ephemeral messages + WebRTC)

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.

src/client/assets/themes/OasisMobile.css

@@ -1082,7 +1082,9 @@ body { padding-top: 66px; }
 .fork-sheet-toggle { position: absolute; width: 1px; height: 1px; opacity: 0; pointer-events: none; margin: 0; }
 
 .hive-sheet {
-  position: fixed; inset: 0; z-index: 1200; pointer-events: none;
+  position: fixed; inset: 0; z-index: 1200;
+  visibility: hidden;                 /* CERRADA: fuera del hit-testing → el topbar y el contenido de abajo SIEMPRE reciben taps (fix del bug de "botones de arriba no funcionan") */
+  transition: visibility 0s linear .3s;  /* al cerrar, mantiene visible durante la animación de bajada */
   background-color: transparent; box-shadow: none; border-radius: 0; /* anula el div{#222} global */
 }
 .hive-sheet-backdrop { position: absolute; inset: 0; background: rgba(0,0,0,.6); opacity: 0; transition: opacity .25s ease; }
@@ -1095,7 +1097,7 @@ body { padding-top: 66px; }
   box-shadow: 0 -6px 24px rgba(0,0,0,.5);
 }
 /* abierto */
-.fork-sheet-toggle:checked ~ .hive-sheet { pointer-events: auto; }
+.fork-sheet-toggle:checked ~ .hive-sheet { visibility: visible; transition: visibility 0s; }
 .fork-sheet-toggle:checked ~ .hive-sheet .hive-sheet-backdrop { opacity: 1; }
 .fork-sheet-toggle:checked ~ .hive-sheet .hive-sheet-panel { transform: translateY(0); }
 
@@ -1118,3 +1120,65 @@ body { padding-top: 66px; }
 /* el hive dentro de la hoja */
 .hive-sheet .hive-nav { margin: 2px auto 0; max-width: 360px; }
 .hive-sheet .hive-mods { background-color: transparent; box-shadow: none; border-radius: 0; } /* por si el div{#222} lo alcanza */
+
+/* topbar v2: solo identidad (logo … avatar); el spacer empuja el avatar a la derecha */
+.oasis-mobile-topbar .omt-spacer {
+  flex: 1 1 auto; min-width: 0;
+  background-color: transparent; box-shadow: none; border-radius: 0; padding: 0; margin: 0; /* anula div{#222} */
+}
+
+/* control segmentado Personal/Community/Todo dentro de la hoja (movido desde el topbar) */
+.hive-sheet-seg {
+  display: flex; gap: 6px; margin: 2px 0 10px;
+  background-color: transparent; box-shadow: none; border-radius: 0; /* anula div{#222} */
+}
+.hive-sheet-seg .hs-seg {
+  flex: 1 1 0; text-align: center;
+  min-height: 40px; display: flex; align-items: center; justify-content: center;
+  border: 1px solid #FFD700; border-radius: 10px;
+  background: #161616; color: #FFD700; font-weight: 600; font-size: 13px;
+  text-decoration: none;
+}
+.hive-sheet-seg .hs-seg.active { background: #FFD700; color: #121212; }
+
+/* ==========================================================================
+   FORK_IA_UX · Módulo KARVAN (mensajes temporales + WebRTC) — chat estilo burbujas
+   ========================================================================== */
+.karvan-intro h2 { color: #FFD700; margin: 0 0 6px; }
+.karvan-sub { color: #FFDD44; font-size: 13px; }
+.karvan-create input[type="text"] { width: 100%; box-sizing: border-box; padding: 10px 12px;
+  background: #161616; border: 1px solid #333; border-radius: 10px; color: #FFD700; }
+.karvan-ttl { display: flex; align-items: center; flex-wrap: wrap; gap: 10px; margin: 10px 0; }
+.karvan-ttl-lbl { color: #FFDD44; font-size: 13px; }
+.karvan-ttl-opt { display: inline-flex; align-items: center; gap: 4px; color: #FFD700; font-size: 13px; }
+.karvan-create button, .karvan-compose button { padding: 10px 16px; border: 1px solid #FFD700;
+  border-radius: 10px; background: #FFD700; color: #121212; font-weight: 700; cursor: pointer; }
+.karvan-rooms { list-style: none; margin: 8px 0 0; padding: 0; }
+.karvan-rooms li { margin: 0 0 8px; }
+.karvan-room-item { display: flex; justify-content: space-between; align-items: center; gap: 10px;
+  padding: 12px 14px; background: #161616; border: 1px solid #333; border-radius: 12px;
+  color: #FFD700; text-decoration: none; min-height: 48px; box-sizing: border-box; }
+.karvan-room-item .kr-title { font-weight: 600; }
+.karvan-room-item .kr-meta { color: #FFDD44; font-size: 12px; white-space: nowrap; }
+.karvan-empty { color: #FFDD44; }
+
+/* sala */
+.karvan-room-head { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
+.karvan-back { color: #FFD700; text-decoration: none; font-weight: 600; }
+.karvan-room-title { flex: 1 1 auto; color: #FFD700; font-weight: 700; text-align: center;
+  overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.karvan-expire { color: #FFDD44; font-size: 12px; white-space: nowrap; }
+.karvan-live { display: inline-flex; align-items: center; gap: 6px; color: #FFDD44; font-size: 12px; margin-bottom: 8px; }
+.karvan-live .kl-dot { width: 8px; height: 8px; border-radius: 50%; background: #777; }
+.karvan-live.on .kl-dot { background: #35d07f; }
+.karvan-live.on .kl-txt { color: #35d07f; }
+.karvan-msgs { list-style: none; margin: 0; padding: 6px 0; display: flex; flex-direction: column; gap: 6px;
+  max-height: 58vh; overflow-y: auto; }
+.karvan-msg { max-width: 82%; align-self: flex-start; background: #1c1c1c; border: 1px solid #333;
+  border-radius: 14px; padding: 7px 11px; box-sizing: border-box; }
+.karvan-msg-self { align-self: flex-end; background: #2a2412; border-color: #FFD700; }
+.karvan-msg .km-from { display: block; font-size: 10px; color: #FFDD44; margin-bottom: 2px; }
+.karvan-msg .km-text { color: #FFD700; word-break: break-word; }
+.karvan-compose { display: flex; gap: 8px; margin-top: 10px; }
+.karvan-compose input[type="text"] { flex: 1 1 auto; min-width: 0; padding: 10px 12px;
+  background: #161616; border: 1px solid #333; border-radius: 10px; color: #FFD700; }