UX-02: the panel was weaker than the startup gate for one field

Applying review finding N1, which was non-blocking because it fails closed, and
N2, which is a fabricated number.

N1. Clearing the `max_w` box answered HTTP 500 on a non-JSON body, which the
page rendered as "cannot reach the add-on" - untrue, and for the most prominent
limit field's most likely transient state. The cause was a disagreement between
two files that `inverter.py`'s own docstring says to keep in step:

  validate.py `_number()`  reads "" as "use the default", so rule 9 saw 2000
                           and was content
  inverter.py line 515     did a bare `float(opts.get("max_w", 2000))`, which
                           raises ValueError on ""

So a shape rule 9 TOLERATED could not be composed at all - the docstring's rule
inverted. The roster path never had this: `_entry_max_w` already guards. Only
the flat single-inverter path did. `_flat_max_w()` now reads empty as the
default exactly as `_number()` does, and unparseable as 0.0 exactly as
`_entry_max_w` does, where rule 9 refuses it by name at line 790.

⚠️ THE FIRST ATTEMPT AT THIS MADE IT WORSE, AND THE PROBE CAUGHT IT. Guarding
`build_roster` in `selfconfig` with `except: return validate(opts), []` turned
the 500 into ZERO PROBLEMS for `max_w: ""` - the validator has nothing to say
about it, so an empty list came back and the page would have ENABLED SAVE. A
crash became a silent acceptance. The guard is kept as a backstop for shapes
neither file anticipates, but it can no longer return an empty list: if the
roster cannot be composed and the validator names no reason, that disagreement
is itself reported.

MEASURED after the fix, `problems_and_ranges` with no HA:
  max_w 5000, slew_w 400   0 problems      (the live shape)
  max_w "",   slew_w 400   1 problem       rule 10, "against a site rail of
                                           2000 W" - clearing the box FAILS
                                           CLOSED on the live install rather
                                           than silently halving the rail
  max_w "",   slew_w 0     0 problems      accepted at the 2000 default
  max_w "abc"              1 problem       "max_w 'abc' is not a number"
Before the fix, both "" and "abc" raised ValueError instead.

N2. `translations/en.yaml:7` said "all 71 keys ... so ALL SEVENTY are rendered".
The 70->71 correction had been made in one half of the sentence and not the
other. 59-of-71 required is correct and was re-measured.

Suite: 24 files, all pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU

goodwe_controller/app/selfconfig.py

@@ -304,7 +304,36 @@ async def problems_and_ranges(opts: dict, hass=None):
     one. That was the first shape of this and it disagreed with itself.
     """
     flat = str(opts.get("setpoint_entity", "") or "").strip()
-    units = build_roster(opts, None)
+
+    # ⚠️ THE ROSTER IS BUILT BEFORE THE VALIDATOR RUNS, AND IT PARSES NUMBERS.
+    # `build_roster` reaches `inverter.py`'s `float(opts.get("max_w", 2000))`,
+    # which raises on a value the validator has a SENTENCE for. Cleared the
+    # `max_w` box and the panel answered HTTP 500 - not JSON, so the page said
+    # "cannot reach the add-on", which was untrue - while `validate.py`'s
+    # "max_w ... is not a number" was unreachable through the panel and reachable
+    # at startup, where `main.py` validates before it composes. That made this
+    # surface WEAKER than the startup gate for one field, which is the opposite
+    # of what this module claims below.
+    #
+    # A malformed scalar therefore falls back to validating WITHOUT device
+    # bounds. Those bounds come from the roster, and there is no roster; the
+    # validator's own complaint about the unparseable value is the answer the
+    # operator needs, and it is strictly more informative than a 500.
+    try:
+        units = build_roster(opts, None)
+    except (TypeError, ValueError) as exc:
+        # ⚠️ AND IT MUST NOT RETURN AN EMPTY LIST. An empty list means "no
+        # problems", and the page enables Save on it. If the roster could not be
+        # composed at all and the validator has nothing to say about why, that
+        # disagreement is itself the finding - so it is reported rather than
+        # swallowed. Returning `[]` here would turn a crash into a silent
+        # acceptance, which is worse than the 500 this replaced.
+        found = list(validate_startup_config(opts))
+        if not found:
+            found = [f"the configuration could not be composed ({type(exc).__name__}: "
+                     f"{exc}), and the validator did not name a reason. This is a "
+                     f"disagreement between the two and should be reported."]
+        return found, []
     if hass is not None:
         async def _limits(unit):
             if unit.setpoint_entity: