added more diagnostics

meshtastic_receiver/DOCS.md

@@ -7,6 +7,8 @@ the results in Home Assistant via MQTT Discovery:
   `to`, and timestamp as attributes).
 - **Parsed sensors** — values pulled out of structured messages such as
   `🏠 T1:20.8°C T2:26.7°C H1:83.7%` become individual numeric sensors.
+- **Link diagnostics** — `Last Seen`, `RSSI`, `SNR`, and `Hops Away`, derived
+  from each packet's metadata (shown under the device's Diagnostic section).
 
 This is the receiving counterpart to the **Meshtastic Sensor Broadcaster** add-on.
 
@@ -44,11 +46,23 @@ ignored). For example:
 produces `T1=20.8`, `T2=26.7`, `T3=26.6`, `H1=83.7`, `H2=54.4`, `H3=55.5`,
 each published to the sensor configured with that `label`.
 
+## Link diagnostics
+
+These are created automatically (no config) from each received packet:
+
+| Sensor | Source | Notes |
+|--------|--------|-------|
+| `Last Seen` | packet `rx_time` | Updates on every packet on the channel. |
+| `RSSI` | packet `rx_rssi` (dBm) | Signal at the gateway. Omitted when the gateway originated the packet (value 0). |
+| `SNR` | packet `rx_snr` (dB) | Published alongside RSSI. |
+| `Hops Away` | `hop_start - hop_limit` | Number of hops the packet traveled. Requires firmware that reports `hop_start`. |
+
 ## Topics used
 
 - Discovery: `{discovery_prefix}/sensor/{device}/{label}/config`
 - State: `meshtastic_receiver/{device}/{label}`
 - Last message: `meshtastic_receiver/{device}/last_message` (+ `/attributes`)
+- Diagnostics: `meshtastic_receiver/{device}/{last_seen,rssi,snr,hops_away}`
 - Availability: `meshtastic_receiver/{device}/status`
 
 ## Privacy note