feat(common): sports_live_fetch -- the reconciled live fetch and odds (sports family 9) (#793)

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

@@ -29,8 +29,28 @@ accepts both, but the store flags the old spelling as deprecated
   web interface still starts on boot either way. Hidden when the unit's state
   cannot be read (not installed, or no systemd).
 
+### 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