LoRa Scanner: a MeshCore preset, and its packets read

- MeshCore joins the presets (EU/UK Narrow: 869.618 MHz, 62.5 kHz, SF8,
  CR 4/8, sync 0x12), after the Meshtastic ones so stored choices keep
  their number; `lora preset MeshCore` on the console
- lib/meshcore reads what MeshCore sends in clear: header, path, and a
  node's advert (name, kind, key, position)
- the list row, the details, a Capture's viewer and the console echo read
  a packet by the sync word it was received on
- the bandwidth is printed as 62.5, not 62

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk

lib/core/src/app_keys.h

@@ -188,7 +188,7 @@ inline constexpr KeyHelp kGeminiAnswer[] = {
 inline constexpr KeyHelp kLora[] = {
     {"; .", "up, down"},
     {"Enter", "the packet's details"},
-    {"p", "pick a Meshtastic preset"},
+    {"p", "pick a preset"},
     {"c", "start a Capture, or stop it"},
     {"Tab", "the Sweep"},
 };