fix(eink): queue input so a burst of taps survives a blocking refresh

The joystick directions and Back were never begin()'d, so on the e-ink build
they never claimed a GPIOTE channel — edges landing during a blocking panel
refresh were lost and the IRQ-capture work didn't reach them. begin() them.

Even with edges captured, rapid taps of one direction replayed into a single
check() and collapsed into a double/triple-click event the navigation handler
ignores, and the loop only ever dispatched one key per render. So:

- MomentaryButton: for multiclick=false buttons emit one CLICK per completed
  release (one per check() call) instead of collapsing — each tap stays a
  discrete key. multiclick=true buttons (double/triple) are unchanged.
- UITask: add a key FIFO; drain each direction fully into it, apply the whole
  queued burst, then redraw once. N taps captured during a refresh become N
  navigation steps at the cost of a single refresh. Also fixes losing a key
  when two buttons fire in the same loop iteration.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/companion_radio/ui-new/UITask.h

@@ -149,6 +149,17 @@ class UITask : public AbstractUITask {
   char handleDoubleClick(char c);
   char handleTripleClick(char c);
 
+  // Key FIFO: a burst of taps captured during a blocking refresh (e-ink) is
+  // drained from the buttons into this queue, then all keys are applied before
+  // a single redraw — so rapid navigation steps neither get lost nor cost one
+  // slow refresh each. Also fixes losing a key when two buttons fire in the
+  // same loop iteration.
+  static const uint8_t KEY_QUEUE_SIZE = 16;
+  char _key_queue[KEY_QUEUE_SIZE];
+  uint8_t _kq_head = 0, _kq_tail = 0;
+  void enqueueKey(char c);
+  bool dequeueKey(char& c);
+
   void setCurrScreen(UIScreen* c);
 
 public: