feat(mesh): operator-configurable Meshcore LoRa PHY params (freq/bw/sf/cr)

Archy set no radio params on Meshcore devices — SF/CR/BW/freq lived only in
device firmware, so a radio on the wrong preset could not be fixed from the
node (it hears RF energy but demodulates nothing; the fleet hit exactly this
on an RNode: docs/RETICULUM-TRANSPORT-PROGRESS.md item 4).

- protocol.rs: build_set_radio_params — wire format verified against the
  MeshCore companion firmware handler (CMD_SET_RADIO_PARAMS=11:
  [11][freq:u32 LE MHz*1000][bw:u32 LE kHz*1000][sf][cr]); byte-layout test
  pinned to the Portugal preset 869.618 MHz / 62.5 kHz / SF8 / CR8.
- serial.rs: MeshcoreDevice::set_radio_params (device reboots on OK).
- MeshConfig.lora_radio_params: Option — None (default) leaves the radio
  untouched, so only explicitly-configured deployments are affected.
- session.rs: provision on connect, gated on a persisted last-applied marker
  (SELF_INFO offsets shift across firmware versions) + the same attempt cap
  as region/channel so a refusing radio never reboot-loops.
- mesh.configure RPC: lora_radio_params arm with firmware-range validation.

mesh tests: 114/114 pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/archipelago/src/mesh/mod.rs

@@ -322,6 +322,22 @@ pub(crate) async fn seed_federation_peers_into_mesh(
     }
 }
 
+/// Operator-configured LoRa PHY parameters for a Meshcore radio, in the
+/// firmware's own field units: `freq_khz` = MHz×1000 (869618 → 869.618 MHz),
+/// `bw_hz` = kHz×1000 (62500 → 62.5 kHz), `sf` 5..=12, `cr` 5..=8. These are
+/// region/deployment-specific (e.g. the Portugal preset 869618/62500/8/8) and
+/// MUST match every radio on the local mesh — a mismatched radio hears RF
+/// energy but demodulates nothing. None (the default) leaves the device's own
+/// settings untouched, so nodes outside the configured deployment are never
+/// affected.
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
+pub struct LoraRadioParams {
+    pub freq_khz: u32,
+    pub bw_hz: u32,
+    pub sf: u8,
+    pub cr: u8,
+}
+
 /// Mesh configuration (persisted to disk).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct MeshConfig {
@@ -340,6 +356,11 @@ pub struct MeshConfig {
     /// unset/None.
     #[serde(default)]
     pub lora_region: Option<String>,
+    /// Meshcore LoRa PHY parameters (freq/bw/sf/cr). Provisioned onto the
+    /// radio on connect when set; None leaves the device untouched. Ignored
+    /// for Meshtastic (region/preset covers it) and Reticulum.
+    #[serde(default)]
+    pub lora_radio_params: Option<LoraRadioParams>,
     /// Whether to periodically broadcast our identity.
     #[serde(default)]
     pub broadcast_identity: bool,
@@ -422,6 +443,7 @@ impl Default for MeshConfig {
             device_path: None,
             channel_name: Some("archipelago".to_string()),
             lora_region: None,
+            lora_radio_params: None,
             broadcast_identity: true,
             advert_name: None,
             mesh_only_mode: None,
@@ -722,6 +744,7 @@ impl MeshService {
             self.our_x25519_pubkey_hex.clone(),
             self.server_name.clone(),
             self.config.lora_region.clone(),
+            self.config.lora_radio_params,
             self.config.channel_name.clone(),
             self.config.device_kind,
             self.config.reticulum_tcp.clone(),