feat(common): sports_live_fetch -- the reconciled live fetch and odds (sports family 9)

New hardware-free module src/common/sports_live_fetch.py, copied from
ledmatrix-plugins claude/family9-reconcile once the nine scoreboards made
_fetch_todays_games (seven bodies when measured) and _fetch_odds (three) one
body each. Both live on the plugins' SportsCore, so one mixin,
SportsLiveFetchMixin, carries exactly those two plus the odds worker
_drain_odds_queue; no manager gains a method it lacks today.

Owner decisions (2026-10-12):
- Live scores are always fresh: every poll asks ESPN through
  get_espn_scoreboard and leaves the answer under the shared
  espn_scoreboard_cache_key for its dates (max_age=1: only a copy another
  reader fetched within the last second is reused). The plugins' 30 s
  <sport_key>_scoreboard_current cache is gone.
- College basketball is asked by date like every other league (ESPN
  answered single dates for both college leagues on 2026-10-12).
- Odds never block update(): one daemon worker per manager answers a queue
  and attaches each line in place under _games_lock; one batch in flight per
  manager, games queued meanwhile join it, every dict queued for an id gets
  the one answer. show_odds, the two odds intervals and a missing odds
  manager (debug, not ERROR) are respected.
- An answer whose events is not a list is no games.

Fix: get_espn_scoreboard() no longer caches an answer whose events is not a
list ("events": null), which every reader of the shared key inherited; it is
still returned to the caller.

- test/test_sports_live_fetch.py: the plugins' pinned cases (requests,
  dates and keys at 10:00 and 02:00 Eastern, freshness, malformed and failed
  answers, odds that never block and land later, the intervals, one batch per
  manager, a worker that cannot start, update and display on two threads),
  plus the host contract. Mutation-checked (11 mutants, all caught).
- test/test_sports_live_fetch_parity.py: with LEDMATRIX_PLUGINS, compares
  each body with every plugin copy. Passes against claude/family9-reconcile;
  fails against the pre-reconcile tree.
- test/test_espn_scoreboard_cache.py: the null-events regression.
- mypy ratchet, src/common/README.md, CHANGELOG (Unreleased: New modules,
  Fixes), docs/SPORTS_UNIFICATION.md family 9 status and decisions.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -19,8 +19,28 @@ accepts both, but the store flags the old spelling as deprecated
 
 ## Unreleased
 
+### New modules
+
+- `src/common/sports_live_fetch.py` -- sports consolidation family 9, once the
+  plugins made `_fetch_todays_games` (seven bodies) and `_fetch_odds` (three)
+  one each: `SportsLiveFetchMixin` (`SportsCore`), with the odds worker
+  `_drain_odds_queue` beside them. The live poll asks ESPN on every poll
+  (a copy another reader fetched within the last second is reused) and
+  leaves the answer under the shared `espn_scoreboard_cache_key` for its
+  dates; college basketball is asked by date like every other league; an
+  answer whose `events` is not a list counts as no games. Odds never block
+  `update()`: one daemon worker per manager answers a queue and attaches each
+  line in place under `_games_lock`, one batch in flight at a time. A plugin
+  may inherit the mixin once it floors on the release that ships it, and
+  deletes its copies then.
+
 ### Fixes
 
+- `get_espn_scoreboard()` no longer caches an answer whose `events` is not a
+  list (ESPN has sent `"events": null`): every reader of the shared scoreboard
+  key -- odds-ticker, the other scoreboards -- inherited it until it aged out.
+  The answer is still returned to the caller as it came.
+
 - `SportsRankingsMixin` (#789's deferred review points, now that it is the
   only copy): a poll entry whose `current` cannot be converted to an
   integer (`None`, a non-numeric string) is skipped instead of throwing