fix(ui): restore talkie idle vs active animation

The previous talkie-overlay refactor lost the rest/active behaviour and
left the radio-shake CSS animation running constantly. Restore the
intended polish:

- Position lerp between TALKIE_REST_Y (idle) and TALKIE_ACTIVE_Y
  (raised when narrator is speaking) with a subtle floating bob.
- Subtle z-axis float at idle, faster shake when active.
- Gate the CSS radio-shake on the new --active modifier so the talkie
  is calm when no narrator dialogue is playing.
- Keep the face-camera rotation [0.18, PI, -0.08] from the original
  overlay version.

Visibility still kicks in at the reveal step (no regression on the
recent fix).

src/index.css

@@ -1257,10 +1257,13 @@ canvas {
 .talkie-dialogue-overlay__model-frame {
   position: absolute;
   inset: 0;
-  animation: talkie-radio-shake 1s ease-in-out infinite;
   filter: drop-shadow(0 16px 22px rgba(0, 0, 0, 0.55));
 }
 
+.talkie-dialogue-overlay--active .talkie-dialogue-overlay__model-frame {
+  animation: talkie-radio-shake 1s ease-in-out infinite;
+}
+
 .talkie-dialogue-overlay__model-frame canvas {
   width: 100% !important;
   height: 100% !important;