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

src/base_classes/sports/capabilities/__init__.py

@@ -0,0 +1,32 @@
+"""Opt-in capabilities for the sports scoreboards.
+
+Each module here is a feature that only *some* sports want. They are composed
+by inheritance (mixins) or selected by name (strategies) — never enabled by an
+``if self.<feature>_enabled:`` branch inside the base classes.
+
+The distinction matters: hockey has no celebrations, so ``HockeyLive`` does not
+inherit :class:`~.celebrations.CelebrationMixin` and the celebration code is not
+in hockey's MRO at all. A bug in it cannot reach a plugin that never opted in.
+
+See ``docs/SPORTS_UNIFICATION.md`` for the full rationale.
+"""
+
+from .celebrations import CelebrationMixin
+from .rotation import (
+    RotationStrategy,
+    SimpleRotation,
+    SmoothWeightedRotation,
+    WeightedCycleRotation,
+    get_rotation_strategy,
+    register_rotation_strategy,
+)
+
+__all__ = [
+    "CelebrationMixin",
+    "RotationStrategy",
+    "SimpleRotation",
+    "SmoothWeightedRotation",
+    "WeightedCycleRotation",
+    "get_rotation_strategy",
+    "register_rotation_strategy",
+]