fix: standardise sensor module structure and docs

- Use multi-line ensure_python_modules list format in ens210.py,
  matching the established pattern from ina219.py
- Fix auto_install_packages indentation in ina219.py docstring
- Remove smbus2 from pyproject.toml core dependencies; sensor packages
  are handled at runtime via ensure_python_modules/auto_install_packages
- Update docs/adding_sensors.md template and guidance to match

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/adding_sensors.md

@@ -58,7 +58,11 @@ class MySensor(SensorBase):
         self.some_option = self.settings.get("some_option", "default")
 
         self.available = False
-        if not self.ensure_python_modules([("import_name", "pip-package-name")]):
+        if not self.ensure_python_modules(
+            [
+                ("import_name", "pip-package-name"),
+            ]
+        ):
             return  # logs a warning; sensor will report unavailable
 
         try:
@@ -87,7 +91,7 @@ Key rules:
 
 - **`sensor_type`** class attribute must match the string passed to `@SensorRegistry.register`.
 - **`self.settings`** is the `settings:` block from the sensor's config entry (a plain dict).
-- **`ensure_python_modules`** handles missing dependencies gracefully. Pass a list of `(import_name, pip_package)` tuples. Returns `False` and logs a warning if any are missing and `auto_install_packages` is `false`; installs them if `true`.
+- **`ensure_python_modules`** handles missing dependencies gracefully. Pass a multi-line list of `(import_name, pip_package)` tuples. Returns `False` and logs a warning if any are missing and `auto_install_packages` is `false`; installs them via pip if `true`. Sensor-specific packages belong here — do **not** add them to `pyproject.toml`.
 - **`_read`** must return a flat `dict[str, Any]`. The base class wraps it in a standard envelope (`name`, `type`, `ok`, `timestamp`, `data`, optional `error`).
 - **`_read`** must raise `RuntimeError` on failure — the base class catches it, marks `ok=False`, and logs it without crashing the polling loop.
 - All hardware initialisation belongs in `__init__`, not in `_read`. Keep `_read` fast.

pyproject.toml

@@ -39,7 +39,6 @@ dependencies = [
     "pyserial>=3.5",
     "pyjwt>=2.8.0",
     "ws4py>=0.6.0",
-    "smbus2>=0.4.0",
 ]
 
 

repeater/sensors/ens210.py

@@ -42,7 +42,11 @@ class ENS210Sensor(SensorBase):
         self._poll_attempts = max(1, int(float(self.settings.get("read_timeout_seconds", 1.0)) / self._poll_interval))
 
         self.available = False
-        if not self.ensure_python_modules([("smbus2", "smbus2")]):
+        if not self.ensure_python_modules(
+            [
+                ("smbus2", "smbus2"),
+            ]
+        ):
             return
 
         try:

repeater/sensors/ina219.py

@@ -7,7 +7,7 @@ Config example:
   - type: ina219
     name: "power_monitor"
     enabled: true
-        auto_install_packages: false
+    auto_install_packages: false
     settings:
       i2c_address: 0x40  # Default INA219 I2C address
       max_expected_amps: 2.0