adds round telemetry support

README.md

@@ -97,7 +97,34 @@ reconciliation; this change does not immediately rewrite or restart them.
 Servers with an unknown map retain their existing config behavior. Rollback
 restores the exact prior config bytes.
 
-## Tests
+## Round telemetry experiment
+
+Send `POST /api/telemetry` with `Content-Type: application/json` to the Electric
+Cherry host (port 3000 in local development):
+
+```bash
+curl http://localhost:3000/api/telemetry \
+  -H 'Content-Type: application/json' \
+  -d '{"event":"round_change","round":17,"server":"t5_zombie_prototype_1","players":4}'
+```
+
+The server must already be registered in Electric Cherry. `round` and `players`
+are required nonnegative integers. Success returns HTTP 200 with
+`{ "ok": true, "telemetry": { "server": "...", "round": 17, "players": 4, "receivedAt": "..." } }`.
+Invalid payloads return 400, unknown/destroyed servers 404, and non-JSON content
+types 415. This endpoint uses the app's existing LAN/Tailscale access model;
+there is no API key requirement.
+
+The latest report is saved across app restarts and streamed immediately to the
+dashboard and server detail page, including after browser reconnection. The UI
+labels it as the last reported round with its age: round-change events alone
+cannot detect a stopped script or a match ending. Send the initial round on each
+new match, then each round change. The latest received request wins (including
+lower rounds for new matches); there is no event ordering or history yet.
+Telemetry player counts are displayed with the report and never replace RCON
+occupancy or affect automated restart gates.
+
+## Running tests
 
 ```bash
 npm test