refactor(sports): one reader for element colours and layout offsets

There were two copies of the per-element colour read and three of the
layout-offset read. They had already drifted -- the scroll-card renderer
carries a comment about having ignored offsets its own schema advertised
-- and each new capability had to be added to all of them or silently work
in some places and not others.

All of them now go through src.element_style, which is what carries the
alias handling and the per-mode lookup. That lands immediately for the
nine plugins importing these modules: a scoreboard asking for `score_text`
offsets finds the `layout.score` its users configured, and a Live instance
resolves its own colours through SKIN_MODE without any call site passing a
mode.

_normalize_color learned "#RRGGBB" in the process. The scoreboards' own
readers have always accepted it, so the shared one had to, or consolidating
would have quietly dropped a form users' configs may hold. _coerce_offset
picked up the non-finite guard the scroll-card reader had and the other two
did not.

_get_layout_offset is promoted onto SportsCoreSharedMixin. Each plugin
still carries its own copy in its bundled sports.py, which wins by MRO --
so adopting this is a deletion in the plugin, and until that deletion
nothing changes for it.

Note for whoever runs the suite next: test_display_dirty_tracking.py is
order-dependent. Fifteen of its tests failed in one full run and passed in
the next with no change in between, and pass in isolation. Pre-existing,
unrelated to this, but it makes a full-run diff untrustworthy until it is
fixed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

test/test_sports_card.py

@@ -262,3 +262,53 @@ class TestUnshareElementFonts:
         fonts = {"score": a, "time": b}
         C.unshare_element_fonts(log, fonts)
         assert fonts["score"] is a and fonts["time"] is b
+
+class TestSharedElementReaders:
+    """The scoreboards' colour and offset reads now go through one
+    implementation.
+
+    There were two copies of the colour read and three of the offset read.
+    They had already drifted: the scroll-card renderer carries a comment
+    noting it used to ignore offsets its own schema advertised. Sharing one
+    reader is what lets a fix (or an alias, or a per-mode override) reach
+    the full-screen scorebug and the scroll card together.
+    """
+
+    CONFIG = {
+        "customization": {
+            "score_text": {"text_color": [255, 200, 0]},
+            "status": {"text_color": "#00ff00"},
+            "layout": {"score": {"y_offset": -3}},
+            "modes": {
+                "live": {"score_text": {"text_color": [255, 0, 0]},
+                         "layout": {"score": {"y_offset": 7}}},
+            },
+        },
+    }
+
+    def test_colour_reads_the_configured_value(self, log):
+        assert C.element_color(self.CONFIG, "score_text") == (255, 200, 0)
+
+    def test_hex_colours_are_still_accepted(self, log):
+        """These readers have always taken '#RRGGBB' as well as [r, g, b],
+        so the shared one had to learn it rather than the callers losing it."""
+        assert C.element_color(self.CONFIG, "status") == (0, 255, 0)
+
+    def test_colour_resolves_through_an_alias(self, log):
+        """The style block says status_text where this config says status."""
+        assert C.element_color(self.CONFIG, "status_text") == (0, 255, 0)
+
+    def test_a_mode_overrides_the_colour(self, log):
+        assert C.element_color(self.CONFIG, "score_text",
+                               mode="live") == (255, 0, 0)
+
+    def test_an_unset_element_gets_the_default(self, log):
+        assert C.element_color(self.CONFIG, "nothing", (1, 2, 3)) == (1, 2, 3)
+
+    @pytest.mark.parametrize("config", [
+        None, {}, "nonsense", {"customization": "nonsense"},
+        {"customization": {"score_text": "nonsense"}},
+        {"customization": {"score_text": {"text_color": "not a colour"}}},
+    ])
+    def test_a_hostile_config_gives_the_default(self, config, log):
+        assert C.element_color(config, "score_text", (9, 9, 9)) == (9, 9, 9)