feat(mobile): collapsed pill composer and mobile input redesign

Mobile composer redesign: when the keyboard is closed the input collapses
into a narrow pill (sessions, attach, placeholder, mic) with a round
new-session button that fades away on the draft screen. Model and agent
selectors move into a row above the textarea; the draft project/branch
pickers and the attachment menu become searchable bottom sheets reusing
MobileOverlayPanel; a drag handle (also available while dictating) swipes
the composer into and out of a fullscreen mode.

Keyboard-lifecycle hardening: composer controls (agent cycle, dictation
and its overlay controls) no longer steal focus and dismiss the keyboard;
overlays reopen the keyboard on close via a debounced restore chain that
survives menu-to-picker handoffs and skips the native file picker; open
overlays and dictation keep the composer expanded. Dictation starts
directly from the pill and its overlay content fades in after the shape
settles. The keyboard slide compensates the pill-to-full height change in
one motion, and the mobile highlight mirror is disabled so the caret
always matches the text layout.

packages/ui/src/styles/mobile.css

@@ -624,3 +624,21 @@
 :root.oc-capacitor-app.oc-keyboard-open .oc-mobile-composer {
   padding-bottom: 12px;
 }
+
+/* Content cross-fade for the pill ↔ full composer morph. The wrapper animates
+   its height (FLIP in ChatInput); the freshly mounted state fades in on top. */
+@keyframes oc-composer-morph-fade {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+.oc-composer-morph-fade {
+  animation: oc-composer-morph-fade 0.24s ease-out both;
+}
+
+/* Voice overlay variant: the overlay BACKGROUND appears immediately (it rides
+   the morphing shape), but its content stays hidden until the shape has mostly
+   finished growing, then fades in — no clipped controls mid-morph. Timings
+   follow the 340ms wrapper morph in ChatInput. */
+.oc-composer-morph-content-fade > * {
+  animation: oc-composer-morph-fade 0.18s ease-out 0.26s both;
+}