feat(sports): opt-in celebration and rotation capabilities

Phase B2 of the sports unification. Both features exist in only some of
the nine scoreboards, so they ship as capabilities the plugin composes,
never as `if self.<feature>_enabled` branches inside the base classes: a
sport that does not opt in has none of this code in its MRO.

CelebrationMixin (afl, nrl, soccer, football)
The two lineages spelled this differently -- _check_for_goal /
celebrate_opponent_goals vs _check_for_score / celebrate_opponent_scores
-- but the bodies were identical apart from three things, each now a
seam rather than a branch:
  - wording -> score_phrase() / win_phrase() hooks
  - follow-up suppression -> COALESCE_SCORING_SEQUENCE, on for football
    where a touchdown lands as +6 then +1, off where two increments are
    two real goals
  - team identity -> _favorite_key, so nrl matches on team id without
    core learning why its abbreviations are ambiguous
Both config spellings are read, so a plugin adopting the mixin keeps
working with the keys already in its published schema.

Rotation strategies
The three "dialects" turned out to be one algorithm (SWRR) in two
shapes: an incremental picker holding state across calls, and a
precomputed per-cycle list. They agree within a cycle and differ only at
the boundary, so core ships both behind a name registry rather than
declaring a winner. weight_for is supplied by the host, so rotation.py
never learns what a favorite is; an unknown name degrades to "simple"
because it arrives from user config.

Each strategy is checked against a verbatim transcription of the plugin
code it replaces, over every live-game shape up to four games -- the
differential B5 will delete the bundled copies on the strength of.

185 new tests. Gates: 648 core unit, 60 plugin safety.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FgbA8SMutQQpXkMG8LMmC4

.github/workflows/test.yml

@@ -74,4 +74,5 @@ jobs:
             test/test_sports_base_characterization.py \
             test/test_element_style.py \
             test/test_sports_core_promotions.py \
-            test/test_sports_modes_promotions.py
+            test/test_sports_modes_promotions.py \
+            test/test_sports_capabilities.py