obd-poller: OBD-II mode 01, the single CAN writer; recorder keeps its values

obd-poller asks 0x7DF for the nine obd2 signals, only while the bus is alive,
and publishes envelopes stamped with the reply's kernel time. The recorder
subscribes to yukart/vehicle/* and writes vehicle.ndjson beside the frames.
Tested against a fake ECU on vcan0.

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

Cargo.toml

@@ -2,7 +2,7 @@
 name = "svc-core"
 version = "0.1.0"
 edition = "2021"
-description = "Acquisition and processing cluster: recorder and orin-status now; can-bridge, obd-poller, gnss, decoder later"
+description = "Acquisition and processing cluster: recorder, orin-status and obd-poller now; can-bridge, gnss, decoder later"
 publish = false
 
 [[bin]]
@@ -13,6 +13,10 @@ path = "src/recorder/main.rs"
 name = "orin-status"
 path = "src/orin-status/main.rs"
 
+[[bin]]
+name = "obd-poller"
+path = "src/obd-poller/main.rs"
+
 [[bin]]
 name = "bus-bench"
 path = "src/bus-bench/main.rs"