fix(mesh): native E2E DM for archy↔archy text + software radio-reboot

- send_message now sends archy↔archy plain text as a native TEXT_MESSAGE_APP
  DM (firmware PKC-encrypts E2E), not wrapped in the binary typed envelope
  that silently broke archy↔archy LoRa delivery. Archy peers' Sent rows are
  marked encrypted so the E2E pill shows; rich typed msgs still use the
  typed-wire path.
- Add a software radio-reboot to recover a wedged/RX-deaf radio without
  physical access (and for the Device-tab settings panel): driver reboot()
  via AdminMessage reboot_seconds=97 (verified vs meshtastic/protobufs),
  MeshCommand::RebootRadio, MeshService::reboot_radio, RPC mesh.reboot-radio.
- Handoff doc: docs/SESSION-1.8.0-OTA-PROGRESS.md "RESUME HERE" — RF link is
  the proven blocker (radios not hearing each other); modem_preset mismatch
  is the prime suspect; on-device Meshtastic-app check + fix plan documented.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/archipelago/src/mesh/meshtastic.rs

@@ -59,6 +59,10 @@ const FROM_RADIO_MAX: usize = 4096;
 const ADMIN_SET_CONFIG_FIELD: u64 = 34;
 /// AdminMessage.set_channel oneof field number (carries a `Channel`).
 const ADMIN_SET_CHANNEL_FIELD: u64 = 33;
+/// AdminMessage.reboot_seconds oneof field number (int32). Verified against
+/// meshtastic/protobufs admin.proto: `reboot_seconds = 97` (NOT 40 — the
+/// payload_variant numbers jump after the setters).
+const ADMIN_REBOOT_SECONDS_FIELD: u64 = 97;
 /// FromRadio.channel (field 10): a `Channel` streamed during want_config.
 const FROM_RADIO_CHANNEL: u64 = 10;
 const FROM_RADIO_QUEUE_STATUS: u64 = 11;
@@ -383,6 +387,34 @@ impl MeshtasticDevice {
         Ok(())
     }
 
+    /// Reboot the locally-connected radio via `AdminMessage { reboot_seconds }`
+    /// on the ADMIN_APP port — the same local-admin path `set_advert_name` /
+    /// `set_lora_region` use (no session passkey needed over serial). The
+    /// firmware reboots after `seconds`, which clears a wedged / RX-deaf radio
+    /// (a radio that has stopped hearing the mesh while still transmitting) and
+    /// re-runs its LoRa init. The listener's reboot→reconnect loop reopens the
+    /// serial link when it comes back.
+    pub async fn reboot(&mut self, seconds: i64) -> Result<()> {
+        let Some(node_num) = self.node_num else {
+            anyhow::bail!("Meshtastic reboot: node_num unknown");
+        };
+        // AdminMessage { reboot_seconds(97): int32 }. We only ever pass a small
+        // positive delay, which encodes as a plain varint.
+        let mut admin = Vec::new();
+        encode_varint_field_into(ADMIN_REBOOT_SECONDS_FIELD, seconds as u64, &mut admin);
+
+        let packet = encode_mesh_packet(node_num, ADMIN_APP, &admin);
+        self.send_to_radio(&encode_to_radio_variant(TO_RADIO_PACKET, &packet))
+            .await
+            .context("Failed to send Meshtastic reboot admin packet")?;
+
+        info!(
+            node_num,
+            seconds, "Sent Meshtastic radio reboot (device will reboot to recover)"
+        );
+        Ok(())
+    }
+
     /// Provision archy's two channels so the radio works like off-the-shelf
     /// Meshtastic AND carries our private group:
     ///   - slot 0 (PRIMARY)  = the DEFAULT public channel (name "", default key)