feat(ui): phone-style layout for direct calls

The call screen now shows two different layouts depending on
whether the call is a 1:1 direct call or a room/group call:

**Direct call (directCallPeer set):**
- Large centered identicon (96px circular with glow)
- Peer name (22px bold) + fingerprint (11px mono)
- Connection badge: "P2P Direct" (green), "Via Relay" (blue),
  or "Connecting..." (yellow) — auto-detected from the
  call-debug buffer's dual_path_race_won event
- Room name header shows the peer's alias/fp instead of "general"
- Group participant list is hidden

**Room/group call (directCallPeer null):**
- Existing group participant list layout — unchanged

The badge updates live from pollStatus by scanning the debug
buffer for the connect:dual_path_race_won event. If the path
was "Direct" → green P2P badge; if "Relay" → blue relay badge.
Before the race resolves, shows yellow "Connecting...".

directCallView is cleared on showConnectScreen (call end).

CSS in style.css: .direct-call-view, .dc-identicon, .dc-name,
.dc-fp, .dc-badge with .relay and .connecting modifiers.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktop/index.html

@@ -111,6 +111,16 @@
         <div class="level-meter">
           <div id="level-bar" class="level-bar-fill"></div>
         </div>
+        <!-- Direct-call phone layout — shown instead of the group
+             participant list when directCallPeer is set. Centered
+             identicon, name, fp, connection badge. Hidden for
+             room calls (directCallPeer == null). -->
+        <div id="direct-call-view" class="direct-call-view hidden">
+          <div id="dc-identicon" class="dc-identicon"></div>
+          <div id="dc-name" class="dc-name">Unknown</div>
+          <div id="dc-fp" class="dc-fp"></div>
+          <div id="dc-badge" class="dc-badge">Connecting...</div>
+        </div>
         <div id="participants" class="participants"></div>
         <div class="controls">
           <button id="mic-btn" class="control-btn" title="Toggle Mic (m)">