fix(sports): say when the schema cannot be read, instead of failing silently (#520)

_schema_font_size swallowed every exception and cached an empty dict. That is
not cosmetic. With no schema, a configured font size can no longer be compared
against the schema default, so every size is treated as a deliberate user
choice and skips the snap to the font's pixel grid -- which renders
4x6-font.ttf at 6 instead of 7: a 3px-wide glyph instead of 4px.

That shipped. On a 256x64 panel it made the odds, the team records and the date
row hard to read, and it was found by a user counting pixels on a photo of the
panel rather than by anything here. The cause (_plugin_dir returning None under
the real plugin loader) is fixed in #519; this makes the same class of failure
audible next time:

    Orphan: could not read config_schema.json (FileNotFoundError: ...); every
    font size will be treated as user-chosen and will skip its pixel grid
    snap. Font sizes may render a pixel narrow.

The message names the consequence, not just the error, because the error alone
does not suggest "your fonts are a pixel narrow".

Logged rather than raised: an unreadable schema must not stop a plugin
rendering. The cache is built once per class (per schema path in sports_card),
so this cannot repeat per frame.

Scope deliberately small. An audit of the three shared modules found 23 handlers
that swallow and return a default, but all 23 catch specific types -- TypeError,
ValueError, ImportError -- turning bad config values into defaults, which is
what they are for. Of 77 broad handlers across the font and odds paths, 74
already log. Only these two were both broad and silent.

src/common/sports_card.py

@@ -17,10 +17,13 @@ deliberate difference is `crisp_size`, which takes the seven-plugin guard
 the extra guard only stops a None size raising TypeError.
 """
 
+import logging
 from datetime import datetime, timezone
 from typing import Any, Dict, Optional, Tuple
 from zoneinfo import ZoneInfo
 
+logger = logging.getLogger(__name__)
+
 __all__ = [
     "ELEMENT_FOR_FONT", "FAVORITE_RESULT_COLOR_DEFAULTS", "FONT_NAME_ALIASES",
     "FONT_PIXEL_GRID", "MONTH_ABBR", "WEEKDAY_ABBR",
@@ -395,7 +398,14 @@ def schema_font_size(schema_path: str, element_key) -> Optional[int]:
                 size = spec.get('properties', {}).get('font_size', {}).get('default')
                 if size is not None:
                     cache[key] = int(size)
-        except Exception:
+        except Exception as exc:
+            # See sports_shared._schema_font_size: an unreadable schema
+            # silently disables the pixel-grid snap for every element.
+            # Built once per schema path, so this cannot repeat per frame.
+            logger.warning(
+                "could not read %s (%s: %s); font sizes will skip their "
+                "pixel grid snap and may render a pixel narrow",
+                schema_path, type(exc).__name__, exc)
             cache = {}
         _SCHEMA_FONT_SIZE_CACHE[schema_path] = cache
     return cache.get(element_key)