SMA-2: each inverter is reached through a driver; GoodWe behaviour unchanged

app/drivers.py holds one Driver per roster entry (configured, actuator_id,
limits, read, write, release, probe, link_stale_s, batt_bound, settle_s, brand,
words). GoodWeEsphomeDriver makes the calls the code it replaced made, in the
same order. Inverter gets driver; has_writer, is_live and link_note read it. The
SoC/power read, the write, the device range (run_control, amain, the settings
panel), rule 2 per unit and the SAFETY-28 census go through it.

setpoint_entity is optional per entry beside driver, host, port, unit_id and
maintenance; only goodwe_esphome is selectable, the rest are checked and unused.

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

goodwe_controller/config.yaml

@@ -942,11 +942,17 @@ schema:
   # batteries, whereas an absent capacity has an honest answer - no opinion
   # about the split, every unit weighs 1.0, which is what shipped.
   #
-  # ⚠️ FOUR KEYS ARE REQUIRED PER ENTRY AND THAT IS DELIBERATE. An entry with
+  # SMA-2. `driver` empty means goodwe_esphome, the only choice for now.
+  # `host`, `port`, `unit_id` and `maintenance` are accepted and checked for
+  # shape; nothing reads them yet (DECISIONS/SMA-2-driver-seam.md).
+  #
+  # ⚠️ THREE KEYS ARE REQUIRED PER ENTRY AND THAT IS DELIBERATE. An entry with
   # no `name` has no Store namespace and would share another unit's SAFETY-02
-  # latch; one with no `setpoint_entity` is a unit nothing can command; one with
-  # no `max_w` would have to borrow a rating, which is the sibling-grading
-  # defect DEV-02 removed; `bms_soc_floor` is SAFETY-32's (options block above).
+  # latch; one with no `max_w` would have to borrow a rating, which is the
+  # sibling-grading defect DEV-02 removed; `bms_soc_floor` is SAFETY-32's
+  # (options block above). `setpoint_entity` WAS A FOURTH; since SMA-2 it is the
+  # GoodWe driver's own key, so a unit nothing can command is refused by
+  # validate.py rule 9(d) per driver rather than by this schema.
   # The optional keys are the sensors, whose absence honestly means "this unit
   # reports none", and `capacity_kwh`.
   #
@@ -958,13 +964,18 @@ schema:
   # test_inverter.py part 12 asserts the ordering is still hostile.
   inverters:
     - name: str
-      setpoint_entity: str
+      setpoint_entity: str?
       max_w: int(100,5000)
       bms_soc_floor: int(0,50)
       soc_entity: str?
       batt_entity: str?
       batt_invert: bool?
       capacity_kwh: float(0.1,200)?
+      driver: list(goodwe_esphome)?
+      host: str?
+      port: port?
+      unit_id: int(0,247)?
+      maintenance: bool?
 
   estop_fitted: bool
   battery_modes_enabled: bool