README: the decoder's 1 s refresh is for unchanged values, not its update rate

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

README.md

@@ -16,7 +16,7 @@ needed.
 | Binary | Installed as | Does |
 |---|---|---|
 | `recorder` | `yukart-recorder.service` | Raw CAN + GNSS to disk, in sessions, under a storage bound; every `yukart/vehicle/*` value (decoded and OBD-II) beside them |
-| `decoder` | `yukart-decoder.service` | The car's own broadcast frames to named signals (`yukart/vehicle/*`): every `z27ag` signal in contracts' `signals.json`, laid out by its `can` block. Booleans on change, numbers ≤ 20/s, each refreshed once a second; reads only |
+| `decoder` | `yukart-decoder.service` | The car's own broadcast frames to named signals (`yukart/vehicle/*`): every `z27ag` signal in contracts' `signals.json`, laid out by its `can` block. Sent on change (booleans at once, numbers at most every 50 ms); a value that has not changed is re-sent once a second, so svc-gw never marks a steady one stale; reads only |
 | `bus-bench` | not installed: a test tool | Raw CAN and decoded-signal load over MQTT, measured: loss, latency, broker CPU ([report](docs/impl/reports/BUS-BENCH.md)) |
 | `obd-poller` | `yukart-obd-poller.service` | OBD-II mode 01 on the K-line through the Bluetooth ELM327 (address in `/etc/default/yukart-elm`), the single writer to the car; never on CAN. The `obd_*` signals, calibration references (`yukart/vehicle/*`): rpm, speed, throttle, load, MAF, timing, O2 every round; temperatures and trims every 5 s. Lets go of the adapter after a minute of ECU silence |
 | `gnss` | `yukart-gnss.service` | gpsd's fix as single values on `yukart/gnss/*`: fix, speed, heading, position, altitude, satellites |