refactor(radio): chart-first restructure on hsmc 0.3 + soak hardening

Migrate from hsmc 0.2 (local-patched) to hsmc 0.3.0 (crates.io, with
embassy + trace-defmt features). Restructure radio chart and bundle
several adjacent stability changes that need to land together for
soak runs.

Radio chart:
- Booting (default, no handlers) -> Operational (default Unconfigured;
  super-state owning CmdPing/CmdGetInfo/Reset/WedgeDetected handlers
  + Recovering + CheckRecoveryBudget) -> Dead (terminal).
- Cold init's during is structurally un-cancellable.
- radio_task is a 30-line shim that panics if run() returns (chart is
  non-terminating).
- Internal queue capacity bumped 8 -> 32 to cover action-emit bursts.

Host chart:
- Connected splits into WaitingForFirstFrame (default, no timer) +
  Active (chart-owned 1s inactivity timer via on(after) + self-
  transition on FrameReceived). Manual Timer::after + last_frame_at
  removed.

Soak hardening:
- ld/nrf52840-memory.x: app start 0x1000 -> 0x26000 to leave the
  factory s140 SoftDevice dormant in flash.
- hal/nrf52840.rs: dump POWER.RESETREAS on boot -- WARN on DOG/LOCKUP,
  INFO on RESETPIN/SREQ/wake-from-OFF.
- host/usb.rs: read_packet errors discriminated -- Disabled is debug
  (normal during USB enum), BufferOverflow stays warn.
- COBS encode warns now carry type/tag/payload-length for diagnosis.
- RADIO_THROTTLED static initializes to true (no proof of host drain
  at boot).
- driver/sh1106.rs: init retries 3x with 100ms backoff (intermittent
  first-write race on power-up).
- Cargo.toml: unexpected_cfgs allowlist for hsmc's journal/trace-*
  features.

docs/semtech_lora_cad_lbt_guidebook.md: vendor the Semtech CAD/LBT
reference for offline lookup.

src/driver/mod.rs

@@ -1,7 +1,8 @@
 #[cfg(any(
     feature = "wio_tracker_l1",
     feature = "elecrow_thinknode_m2",
-    feature = "lilygo_tbeam_supreme"
+    feature = "lilygo_tbeam_supreme",
+    feature = "rak_wisblock_4631"
 ))]
 pub mod sh1106;
 
@@ -67,7 +68,8 @@ where
 #[cfg(any(
     feature = "wio_tracker_l1",
     feature = "elecrow_thinknode_m2",
-    feature = "lilygo_tbeam_supreme"
+    feature = "lilygo_tbeam_supreme",
+    feature = "rak_wisblock_4631"
 ))]
 impl<I> DisplayBrightness for sh1106::Sh1106<I>
 where

src/driver/sh1106.rs

@@ -37,6 +37,12 @@ impl<I: I2c> Sh1106<I> {
     /// Send a sequence of commands (each prefixed with the I2C command byte 0x00).
     async fn cmd(&mut self, commands: &[u8]) -> Result<(), I::Error> {
         for &c in commands {
+            #[cfg(feature = "debug-twim")]
+            defmt::info!(
+                "[sh1106] cmd write: addr=0x{=u8:02X} bytes=[0x00, 0x{=u8:02X}]",
+                self.addr,
+                c,
+            );
             self.i2c.write(self.addr, &[0x00, c]).await?;
         }
         Ok(())
@@ -44,6 +50,8 @@ impl<I: I2c> Sh1106<I> {
 
     /// Initialize the display with sensible defaults.
     pub async fn init(&mut self) -> Result<(), I::Error> {
+        #[cfg(feature = "debug-twim")]
+        defmt::info!("[sh1106] init: starting");
         self.cmd(&[
             0xAE, // display off
             0xD5, 0x80, // clock div: default
@@ -71,6 +79,8 @@ impl<I: I2c> Sh1106<I> {
         page_buf[0] = 0x40;
 
         for page in 0..PAGES {
+            #[cfg(feature = "debug-twim")]
+            defmt::info!("[sh1106] flush page {=usize}: addr cmds (3 bytes)", page);
             // Set page address and column start (with SH1106 2-column offset).
             self.cmd(&[
                 0xB0 | page as u8,        // page address
@@ -81,6 +91,12 @@ impl<I: I2c> Sh1106<I> {
 
             let start = page * WIDTH;
             page_buf[1..].copy_from_slice(&self.buffer[start..start + WIDTH]);
+            #[cfg(feature = "debug-twim")]
+            defmt::info!(
+                "[sh1106] flush page {=usize}: data write {=usize} bytes (0x40 prefix + 128 pixels)",
+                page,
+                page_buf.len(),
+            );
             self.i2c.write(self.addr, &page_buf).await?;
         }
         Ok(())
@@ -88,6 +104,8 @@ impl<I: I2c> Sh1106<I> {
 
     /// Set display brightness (contrast).
     pub async fn set_brightness(&mut self, value: u8) -> Result<(), I::Error> {
+        #[cfg(feature = "debug-twim")]
+        defmt::info!("[sh1106] set_brightness: 0x{=u8:02X}", value);
         self.cmd(&[0x81, value]).await
     }
 }