UX-13 P0 review: keep unread keys, back off a failed entity read

- uimodel: editing a listed inverter keeps the stored flat keys, and a
  region of "own" keeps a stored price_taxes_profile (both were dropped).
- haentities: a failed read also waits CACHE_S, so polls while Home
  Assistant is down do not queue one 10 s read each.
- ui_text: the Flanders preset names its DSO, and the help says
  Wallonia and Brussels have no figures yet. REGION_PRESETS cites the card.
- tests: decode of a reversed solar row, both kept keys, the backoff.

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

goodwe_controller/app/uimodel.py

@@ -31,7 +31,8 @@ class DeriveError(ValueError):
 # --------------------------------------------------------------------------- #
 # Region presets for "Grid costs, levies and VAT". Year-stamped, updated each
 # January (owner, 2026-09-27). Only presets with a sourced figure are listed:
-# Flanders is app/price.py's Fluvius Antwerpen sum (TARIFF-18). Wallonia and
+# Flanders is app/price.py's Fluvius Antwerpen sum (TARIFF-18: Eneco
+# residential card, Flanders, September 2026, VAT included). Wallonia and
 # Brussels have a day and a night band (config.yaml) and join with sourced
 # figures; until then those sites choose "own".
 # --------------------------------------------------------------------------- #
@@ -93,9 +94,10 @@ def _roster_encode(m, keep):
         return out
     out["inverters"] = [{k: v for k, v in c.items() if v is not None}
                         for c in cards]
+    # The flat keys beside a list are not read: they stay as stored.
+    out.update({k: copy.deepcopy(keep[k]) for k in _ROSTER_FLAT if k in keep})
     if shape == "flat":
         # CFG-04 rule 9e: a flat power request entity beside a list is refused.
-        # The other flat keys stay as stored and are not read.
         out["setpoint_entity"] = ""
     return out
 
@@ -252,7 +254,10 @@ def _region_decode(o):
 def _region_encode(m, keep):
     region = m.get("ui.region")
     if region == OWN:
-        return {"price_taxes_eur_kwh": m.get("price_taxes_eur_kwh")}
+        out = {"price_taxes_eur_kwh": m.get("price_taxes_eur_kwh")}
+        if "price_taxes_profile" in keep:       # "own" keeps the stored table
+            out["price_taxes_profile"] = keep["price_taxes_profile"]
+        return out
     if region not in REGION_PRESETS:
         raise DeriveError(f"unknown region {region!r}")
     p = REGION_PRESETS[region]