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/DECISIONS/SMA-2-driver-seam.md

@@ -0,0 +1,39 @@
+# SMA-2 - each inverter is reached through a driver
+
+**Status: for review.** Tests: `test_sma2_driver.py`. Source: SMA-9 report
+section 1.1. A pure refactor: no behaviour change for GoodWe, no change to a
+command, a log line or a sentence the add-on shows.
+
+Every place that read or steered an inverter used the GoodWe ESPHome entities
+directly, so a second make meant touching all of them. `app/drivers.py` now
+holds one `Driver` per roster entry (`Inverter.driver`): `configured()`,
+`actuator_id()`, `limits()`, `read()`, `write()`, `release()`, `probe()`, and
+`link_stale_s`, `batt_bound`, `settle_s`, `brand`, `words`. `GoodWeEsphomeDriver`
+makes the same calls in the same order as the code it replaced; its
+`release()` is `write(0)`.
+
+**Moved to the driver:** the SoC and power read (`_read_unit`), the write
+(`_write_unit`, still under the SAFETY-28 gate, the clamp, shadow mode and the
+write budget), the device range (`run_control`, `amain`, the settings panel),
+liveness and its window (`has_writer`, `is_live`, `link_note`), the freshness
+bound, the status rows' "is a source set" test, rule 2's per-unit range check
+and SAFETY-28's census. **Not moved:** the clamp, the gate, the heartbeat and
+`command_site_zero()`; stop is still 0 W for every unit, and nothing calls
+`release()` yet (SMA-10). `settle_s` and the control constants are not read
+from the driver yet either: with only GoodWe they would change nothing.
+
+**The seam is not TCP-shaped.** The census asks each entry's driver for its
+actuator id: the setpoint entity for GoodWe, `host:port:unit_id` for a driver
+reached over a socket, so two units behind one gateway are two actuators and
+one unit named twice is the SAFETY-28 refusal. The driver binds its Home
+Assistant on first use by the Controller, so a unit added later is wired too.
+
+**Schema.** `setpoint_entity` is optional per entry (rule 9(d) still requires
+it for GoodWe, with the same sentence), beside `driver` (only `goodwe_esphome`),
+`host`, `port`, `unit_id`, `maintenance`. The last four are checked for shape
+and not read. The Supervisor shape probe was re-run (section K).
+
+**Checked against 23ff9d0:** replay digests and a log of every Home Assistant
+call are byte-identical at N=1 and N=2; the TEL-07 announce diff is 0/0/0; a
+fake driver beside a GoodWe unit allocates, grades, drops and publishes per
+unit; a call site that goes round the seam is caught.