battery: low-battery alert module (v0.13.0)

BatteryAlertModule + BatteryAlertService wired into app.module like
the weather module. Every BATTERY_CHECK_INTERVAL_MS (default 60 s) the
service scans the node state backing GET /api/nodes and broadcasts a
single-packet '⚠️ @!<8-hex> battery low: <X>% (<name>)' alert for every
node at or below BATTERY_ALERT_THRESHOLD percent (default 20, <= on
purpose) not alerted within BATTERY_ALERT_COOLDOWN_MS (default 6 h,
in-memory map — resets on restart). Sends ride the pinned send channel
via MeshService.sendText like every other bot send.

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## v0.13.0 — 2026-09-25 12:34
+
+- New non-AI `src/battery` module: `BatteryAlertModule` + `BatteryAlertService`, wired into `app.module.ts` exactly like the weather module (ScheduleModule.forRoot() + MeshModule). Every `BATTERY_CHECK_INTERVAL_MS` ms (default 60000, read at construction) it scans the same node state that backs `GET /api/nodes` and broadcasts a single-packet alert for every node whose reported battery is at or below `BATTERY_ALERT_THRESHOLD` percent (default 20). The comparison is `<=` on purpose — a node sitting exactly at the threshold counts as low; tests pin this choice.
+- Alert format: `⚠️ @!<8-hex-lowercase-node-num> battery low: <X>% (<longName or shortName>)` — Meshtastic mention syntax (`@!` + zero-padded 8-char lowercase hex, e.g. `@!09a2b3c4`), always well under the ~190-char single-packet limit; the name part falls back longName → shortName and is omitted entirely when the node reported no name. Broadcasts ride the pinned send channel via the existing `MeshService.sendText(BROADCAST_ADDR, text)` path (MESH_SEND_CHANNEL, default index 3) — no new transport.
+- Anti-spam: per-node cooldown of `BATTERY_ALERT_COOLDOWN_MS` ms (default 21600000 = 6 h) in an in-memory `Map<nodeNum, lastAlertEpochMs>` — a node is alerted at most once per window; the map resets on process restart by design (a node may get one duplicate alert after a deploy).
+- Live battery updates: `batteryLevel` was previously only populated from NodeInfo frames during the initial sync. Live NODEINFO_APP packets (port 4, serialized meshtastic.NodeInfo in Data.payload) now update `deviceMetrics` in the node database too — new `decodeNodeInfo()` + `PORT_NODEINFO_APP` in codec.ts, one branch in the existing packet-handling path — so alerts and `/api/nodes` reflect current values between syncs. Unknown nodes get a stub entry when they report metrics live; malformed payloads are skipped like every other port.
+- Tests: new `src/battery/battery.service.spec.ts` (mention hex padding/lowercase, full message construction incl. name fallbacks and the 190-char ceiling, threshold boundary with default + custom env, no-battery skip, once-per-node broadcast target, send-failure never throws, cooldown suppression within window + re-alert after expiry via fake timers) plus a DI spec mirroring weather's; an end-to-end case drives a real MeshService over the fake bridge and asserts the alert frame rides channel index 3 with the exact text. `mesh.service.spec.ts` gains a NODEINFO_APP live-update case (stale sync battery refreshed, other fields preserved, unknown-node stub). All pre-existing specs stay green.
+
 ## v0.12.8 — 2026-09-25 12:04
 
 - Docs (MESHTASTIC.md response protocol): new standing rule per owner request ("remember to always replay on reply on channel when question is send here") — questions received via mesh are **answered on the channel**: every question sent via mesh gets its actual answer broadcast back on the same channel when work completes; an acknowledgement alone is not sufficient, and the answer must not stay only in the private agent session. All existing bullets (always-respond-first, channel-only/no DMs, owner authority 2594370888, language, NO_RESPONSE quirk, self-echo note) unchanged. No code changes — all 64 tests untouched and green.