remove rheemcloud pkg, implement against rest api only

AGENTS.md

@@ -9,14 +9,25 @@ Exporter for Rheem EcoNet / Rheemcloud water heaters, built on the
   `appServices` slice (registers `&econet.EconetService{}`) and the
   `serviceConfig.LoadEnv()` call (see Config gotcha below).
 - `pkg/econet/econet.go` — `EconetService` implements `service.AppService`.
-  It **owns the single `*rheemcloud.Client`** and shares it with the gRPC,
-  MCP, and metrics sub-servers. `Init` connects (fail-fast if creds missing);
-  the returned `ShutdownFunc` stops metrics and closes the client.
+  It **owns the single `econetclient.Client`** and shares it with the gRPC,
+  MCP, and metrics sub-servers. `Init` fails fast if creds are missing, then
+  refreshes device state on a ticker **in a background goroutine** (`pollLoop`,
+  interval `pollInterval`) so a slow or unreachable cloud never blocks
+  HTTP/gRPC server startup. The client is stateless REST, so `ShutdownFunc` is
+  effectively a no-op (the poll goroutine stops on ctx cancel).
+- `pkg/econet/econetclient/` — a minimal EcoNet REST client (ClearBlade
+  backend). `client.go` does the 3 REST calls (auth → `getUserDataForApp` →
+  `dynamicAction` usage) and caches a snapshot under an `RWMutex`; `device.go`
+  decodes the `@...` datapoints into a flat `Device` struct (ported from
+  kevinburke/rheemcloud-go, minus MQTT). `Devices()` is empty until the first
+  `Refresh` succeeds — consumers just see an empty list (no nil-guarding).
+  **No MQTT**, so `WiFiSignal` and `Running`/`RunningState` stay zero.
 - `pkg/econet/econetgrpc/` — `EconetService` gRPC impl (`ListDevices`,
   `GetDevice`) + `deviceToProto`. Does **not** own a client; it's injected.
 - `pkg/econet/econetmcp/` — MCP server at `/api/mcp`; the `list_water_heaters`
   tool delegates to the gRPC server.
-- `pkg/econet/econetmetrics/` — OTEL observable gauges + a usage poller.
+- `pkg/econet/econetmetrics/` — OTEL observable gauges (read the client
+  snapshot at scrape time; no poller of its own).
 
 ## Config gotcha (important)
 
@@ -40,16 +51,16 @@ that's all it takes — no extra wiring.
 
 ## Metrics conventions
 
-- Live state is read at scrape time inside a `RegisterCallback` over
-  `client.Devices()` (cheap, in-memory, always current — the rheemcloud client
-  keeps state fresh over MQTT). Usage (`EnergyUsage`/`WaterUsage`) is REST and
-  slow, so a background poller (`usageInterval`) caches it; the usage callback
-  reads the cache.
+- Live state and usage are both read at scrape time inside `RegisterCallback`s
+  over `client.Devices()` (cheap, in-memory). The `pollLoop` in `econet.go`
+  keeps the snapshot fresh over REST (`client.Refresh`), which folds daily
+  energy/water usage totals into each `Device`. No usage cache or event
+  draining — the callbacks just read the current snapshot.
 - **Attributes**: dotted/namespaced `econet.*` (semantic-convention style),
   low-cardinality only (serial, device_id, friendly_name, type, generic_type,
   mode, energy_type). **Never** put changing values (timestamps) in attributes
   — `econet_last_updated_seconds` is a metric *value*, and it's suppressed
-  until the first MQTT update so it never emits a garbage epoch.
+  until the first refresh so it never emits a garbage epoch.
 - **Units live in metric names** (`_fahrenheit`, `_kwh`, `_gallons`,
   `_dollars`), NOT via `metric.WithUnit` — the OTEL→Prometheus exporter would
   otherwise append a second unit suffix (`..._fahrenheit_F`).
@@ -59,9 +70,9 @@ that's all it takes — no extra wiring.
 - Regenerate proto: `make proto` (buf; `PROTO_DIRS=proto/econet/v1alpha1/*`).
 - Regenerate config schema after config changes: `make schema`.
 - Build/test: `go build ./... && go test ./...`.
-- The rheemcloud `*Device` has no exported constructor, so `deviceToProto`
-  isn't unit-testable in isolation; test the pure helpers (`summarizeDevices`,
-  `b2i`) and exercise the rest with a live run.
+- `econetclient.Device` is a plain struct, so `deviceToProto` and the datapoint
+  decoders (`mode`, `enabled`, `setpoint`, `hotWater`) are unit-testable by
+  hand-building a `Device` or feeding raw JSON to `newDevice`.
 
 ## Live verification (needs a real Rheem account)