obd-poller over the K-line via the Bluetooth ELM327; gnss publisher; elm_connected

obd-poller drops its CAN socket: the Z27AG answers OBD-II only on ISO 9141-2.
It holds a raw RFCOMM link to the ELM (no pairing, no root), fixes the protocol
(ATSP3) so nothing probes CAN, publishes the obd_* signals, and releases the
adapter after a minute of ECU silence so it can sleep.
gnss: gpsd's fix as yukart/gnss/<signal>. orin-status: elm_connected from BlueZ.
One native deploy script (deploy-native.sh BIN) behind the per-service ones;
/etc/default/yukart-elm holds the adapter's address.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

src/orin-status/elm.rs

@@ -0,0 +1,34 @@
+//! The Bluetooth link to the ELM327 (the OBD-II adapter on the K-line), as BlueZ sees
+//! it. Only watched, never opened: the adapter takes one connection, and obd-poller
+//! holds it while the ECU answers.
+
+use std::process::Command;
+
+use serde_json::{json, Value};
+
+pub struct Elm {
+    /// "00:0C:BF:50:AF:3F"; None when no adapter is configured.
+    addr: Option<String>,
+}
+
+/// `bluetoothctl info` says "Connected: yes" while any link to the device is up,
+/// the poller's serial link included. An unknown device is simply not connected.
+fn connected(addr: &str) -> bool {
+    Command::new("bluetoothctl")
+        .args(["info", addr])
+        .output()
+        .map(|o| String::from_utf8_lossy(&o.stdout).lines().any(|l| l.trim() == "Connected: yes"))
+        .unwrap_or(false)
+}
+
+impl Elm {
+    pub fn new(addr: &str) -> Self {
+        Elm { addr: Some(addr.trim().to_string()).filter(|a| !a.is_empty()) }
+    }
+
+    pub fn read(&mut self, out: &mut Vec<(&'static str, Value)>) {
+        if let Some(a) = &self.addr {
+            out.push(("elm_connected", json!(connected(a))));
+        }
+    }
+}