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

CHANGELOG.md

@@ -35,6 +35,20 @@ release that ships it.
   A plugin may start calling these once its manifest floors
   `ledmatrix_min_version` at the release that ships them.
 
+- `src/base_classes/sports/capabilities/` — opt-in capabilities for the sports
+  scoreboards, composed by inheritance rather than gated by config branches
+  inside the base classes:
+  - `CelebrationMixin` — the score/win takeover, merging the goal and score
+    dialects behind the `score_phrase()` / `win_phrase()` hooks, the
+    `COALESCE_SCORING_SEQUENCE` class attribute and the `_favorite_key` seam.
+    Reads both the `celebrate_opponent_goals` and `celebrate_opponent_scores`
+    config spellings. Sports that do not mix it in have none of this code in
+    their MRO.
+  - `RotationStrategy` + a name registry (`swrr`, `weighted`, `simple`,
+    plus `register_rotation_strategy` for plugin-supplied orderings). Each
+    built-in is verified against a verbatim transcription of the plugin
+    implementation it replaces. An unknown name degrades to `simple`.
+
 ### Changed
 - **Live games are no longer dropped when the feed omits a game clock.**
   `SportsLive._is_game_really_over` previously (in the baseball and UFC