WioTrackerL1: redesign companion UI (channels, keyboard, msg preview)

- QuickMsg → Message screen: channel history, on-screen keyboard, custom message first
- Channel history: RAM ring buffer (32 entries, 80 chars), fullscreen view with word-wrap scroll
- After channel send: stay in history, own message shown as "Me: ..."
- MsgPreview: one message per screen with up/down nav, ENTER opens fullscreen scroll
- Monochromatic display: all color usage corrected to DARK/LIGHT only
- Top bar: battery icon, BT muted indicator, splash "Plus for Wio"
- KB_MAX_LEN: 64 → 100 chars; channel text buffer: 52 → 80 chars

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/AbstractUITask.h

@@ -42,5 +42,6 @@ public:
   virtual void msgRead(int msgcount) = 0;
   virtual void newMsg(uint8_t path_len, const char* from_name, const char* text, int msgcount) = 0;
   virtual void notify(UIEventType t = UIEventType::none) = 0;
+  virtual void addChannelMsg(uint8_t channel_idx, const char* text) {}
   virtual void loop() = 0;
 };