UX-13 P4: the setup wizard for installers

The Setup tab draws the Installer view's page model one step at a time,
from each field's `wizard` step in app/uilayout.py: meter (with the kettle
test), inverters and batteries, solar (optional), prices, peak limit
(battery modes: "comes in a later update", OPT-11), check and start.
It reuses P2's controls and saves through /config/validate and
/config/save. No route was added.

- First run: /config/model says `setup_needed` when the stored options name
  no power request entity, or on a new install (no `setup_done` and no
  `auto` in the Store, control not started). The page opens #setup only
  when opened with no route. The wizard's save writes `setup_done`.
- Kettle test: GET ha/entities?entity= reads one entity now, in W. The
  change decides: up keeps meter_invert off, down turns it on; a net or
  import/export meter that goes down blocks the step with what to check.
- Last step: validate.setup_checks() beside the refusals: the meter reads,
  each power request entity exists in HA (bad if not, SAFETY-77), battery
  levels and power with direction, solar sign, prices. Saves with
  shadow_mode on by default, then a confirmed restart naming the 0 W.
- P2 test finding (a): a stale save lists only the keys the other surface
  moved (the blob handed out on open, by fingerprint, against stored now).
- test_setup.py; tools/ux13_wizard_blobs.py makes the 88 blobs the wizard
  can save; all accepted by Supervisor 2026.08.0 AppOptions (offline).
- DECISIONS/UX-13-setup-wizard.md; DOCS "Setup, for a new install".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LyR88rXETvwhTgx6yHE39p

goodwe_controller/test_settings.py

@@ -429,9 +429,11 @@ async def _stale(s, root, sup):
 
 
 _r, _sup = asyncio.run(session(TWO, _stale))
-check("409 with the page fields to look at, and nothing written",
+check("409 with the page fields to look at, and nothing written. Only the "
+      "field the other surface changed, not the page's own edit (P4, P2 "
+      "test finding a)",
       _r[0] == 409 and _r[1]["kind"] == "stale"
-      and "peak_cap_w" in _r[1]["changed_fields"] and _sup.writes == []
+      and _r[1]["changed_fields"] == ["peak_cap_w"] and _sup.writes == []
       and _r[1]["fingerprint"] == selfconfig.fingerprint(_sup.options))
 
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