UX-13 P2 review fixes (PR #145, comment 1880)

1. Discard reloads /config/model: after a stale save the page kept the
   new fingerprint with the old values, so Discard + Save overwrote the
   other surface's change without a 409.
2. Removing cards back to one restores the stored inverter shape, so a
   flat site stays flat after add + remove.
3. A choice the page can only keep ("Other time windows") stays offered
   while it is the stored value.
4. A load locks every locked value again.
5. at_zero() needs an accepted 0 W write; before the first one Home says
   "Going to 0 W" (the heartbeat writes every heartbeat_s, so it clears).
6. A field with a unit drops the translation's "(W)" from its label: the
   peak limit read "Peak limit (W)" beside a kW value.
7. A mirrored choice lists the mirrored field's keys, so a search for
   static_profile finds the contract on a fixed-price site.
8. test_settings: a save refused by ui_to_options writes nothing.

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

goodwe_controller/test_home.py

@@ -123,11 +123,13 @@ MOCK = [.24, .22, .21, .20, .21, .22, .24, .27, .26, .22, .18, .16, .15, .14,
 
 
 def make(opts, *, soc=(62.0, 35.0), batt=(-2500.0, -300.0), grid=10.0,
-         auto=True):
+         auto=True, wrote=0.0):
+    """`wrote` is each inverter's last accepted power request (None: none yet)."""
     c = Controller(dict(opts), _Hass(), _Store(), _Pub(), stop=asyncio.Event())
     c.auto = auto
     for i, inv in enumerate(c.inverters):
         inv.soc, inv.batt = soc[i], batt[i]
+        inv.last_write = wrote
         inv.dev_min, inv.dev_max = -5000.0, 5000.0
     c.grid = grid
     return c
@@ -471,6 +473,11 @@ check("an alarm while the last power request is still 20 W says 'Going to "
 c_sp = make(TWO, auto=False)
 c_sp.inverters[1].last_write = -1500.0
 s_sp = status(c_sp)
+s_new = status(make(TWO, auto=False, wrote=None))
+check("...and before any power request was accepted (just started, or every "
+      "write refused) it says 'Going to 0 W', not 'Held'",
+      [b["now"] for b in s_new["batteries"]]
+      == ["Going to 0 W while control is stopped."] * 2)
 check("...and a stop does the same, per battery",
       [b["now"] for b in s_sp["batteries"]]
       == ["Held at 0 W while control is stopped.",