OPT-11 P2: HA entities for battery modes

Each battery gets an MQTT-discovered Mode select and Use switch, only while
battery_modes_enabled is true. Commands go through handle_action(), the
/action path; refusals are logged once. Retained commands are never applied.
Turning modes off removes exactly the configs announced (kept in the store).
With modes off the announcement is byte-identical to ed739d4.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/test_messages.py

@@ -845,7 +845,7 @@ DATA = {
     "main.py:'cancelled' if task.cancelled() else repr(exc) if exc else 'returned'",
     "main.py:EXIT_CONTROL_DIED", "main.py:first.name", "main.py:OPTIONS_PATH",
     "main.py:err", "main.py:', '.join(sorted(stranded))",
-    "main.py:sorted(on_roster)", "main.py:inv.name",
+    "main.py:sorted(on_roster)", "main.py:inv.name", "main.py:topic_s",
     "main.py:inv.batt_fresh.bound.release_s", "main.py:inv.batt_fresh.bound.move_w",
     "main.py:inv.batt_fresh.bound.unchanged_s", "main.py:inv.batt_fresh.held",
     "main.py:value", "main.py:float(value)",
@@ -1058,6 +1058,8 @@ TEXT = {
     "main.py:rep.explain()": _migration_texts,
     "store.py:rep.explain()": _migration_texts,
     "main.py:plan.words": _tariff_texts,
+    # OPT-11 P2: why an MQTT command was ignored.
+    "main.py:why": lambda: list(messages.PACK_REFUSED.values()),
     # Families: every builder of the text, as a template.
     "main.py:refusal": lambda: (_static(("main.py", "return", "write_refusal"))
                                 + _static(("allocator.py", "return", "authorises"))),