docs: add seven-day analyzer telemetry filter

docs/telemetry_decoder.md

@@ -70,6 +70,37 @@ shows `fault=prefs`, and manual sends return an error instead of acknowledging
 work that cannot run. Such a storage fault must be repaired before settings
 can be changed; the firmware does not overwrite an unmigrated legacy file.
 
+## Find telemetry packets
+
+[Open the seven-day telemetry view in CascadiaMesh Analyzer](https://analyzer.cascadiamesh.org/#/packets?timeWindow=10080&filter=type%20%3D%3D%20RAW_CUSTOM%20%26%26%20size%20%3E%20120%20%26%26%20age%20%3C%207d%20%26%26%20%28payload.raw%20starts_with%20%2254544231%22%20%7C%7C%20payload.raw%20starts_with%20%2254564231%22%20%7C%7C%20payload.raw%20starts_with%20%2249564231%22%20%7C%7C%20payload.raw%20starts_with%20%224E314231%22%20%7C%7C%20payload.raw%20starts_with%20%224E324231%22%29).
+The link selects RAW_CUSTOM packets larger than 120 bytes whose data starts with
+any of the five telemetry prefixes below. To use the filter box directly, paste
+this as one line:
+
+```text
+type == RAW_CUSTOM && size > 120 && age < 7d && (payload.raw starts_with "54544231" || payload.raw starts_with "54564231" || payload.raw starts_with "49564231" || payload.raw starts_with "4E314231" || payload.raw starts_with "4E324231")
+```
+
+| Data | Payload tag | Hex prefix |
+|---|---|---|
+| Temperature | `TTB1` | `54544231` |
+| Battery voltage | `TVB1` | `54564231` |
+| External I2C voltage | `IVB1` | `49564231` |
+| Main-radio noise floor | `N1B1` | `4E314231` |
+| Radio2 noise floor | `N2B1` | `4E324231` |
+
+`&&` requires every condition; `||` accepts any listed prefix. `size` includes
+headers and routing bytes. Use `payload.rawLength > 120` to filter on data length
+instead, or remove `size > 120 &&` to include shorter snapshots.
+`payload.raw` starts at the application data, after the routing bytes.
+
+The URL uses `timeWindow=10080` (seven days in minutes). The explicit
+`age < 7d` condition preserves that cutoff when refreshing, since the analyzer's
+time dropdown only offers fixed windows up to 24 hours. Packet retention and
+loading limits still apply: the current server returns at most 10,000 packets,
+and mobile clients load at most 1,000, so a busy network may show less than a
+full week.
+
 ## Decode a packet
 
 If you are reading this on GitHub, [open the working decoder on the documentation