M3 step 1: RadioLib and lora probe

The probe finds the SX1262 (TCXO 1.8 V works) and measures the antenna
path: the Cap's PI4IOE5V6408 at 0x43 must drive P0 high, or the receiver
is deaf (-111.9 dBm flat vs -87 to -94 dBm with P0 high). DIO2 makes no
difference to reception. Receive only; the radio is left asleep.

RadioLib 7.8.1 + probe: +23.6 KB flash, +656 B static RAM (release).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/platform/lora_probe.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <Print.h>
+
+namespace roro {
+
+// `lora probe` (M3 step 1, Q91): finds the SX1262 on the Cap and how its oscillator and antenna
+// switch are wired, by measuring. Receive only; leaves the radio asleep.
+void loraProbe(Print& out);
+
+}  // namespace roro