fix(espn): fetch a window's edge months whole, cap chunk requests per process (#751)

- fetch_espn_date_chunks() asks for a window's partial edge month whole when the window covers ESPN_MONTH_COVER_MIN_DAYS (7) or more of its days, trimmed to the window by US Eastern start date. New espn_request_chunks().
- Chunk requests share one process-wide cap of ESPN_CHUNK_WORKERS (6) in flight.
- A new process starts as if a range had just been rejected, so it no longer spends a doomed 400 per window at start.
- Also: _eastern_zone() without try/except/pass (Codacy), and test_on_demand_live_and_restore reads the last on-demand state write rather than the last cache write (the font-usage publisher raced it; main CI had failed on it since #748).

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

src/common/README.md

@@ -109,8 +109,11 @@ and the plugin test harness all use it. Most plugins get BDF text through
 [`espn_dates.py`](espn_dates.py). ESPN's site API rejects `dates=` ranges
 and truncates results when `limit` is above 500. `fetch_espn_scoreboard()`
 splits a range into month and day requests ESPN accepts and merges the
-results; `espn_date_chunks()`, `fetch_espn_date_chunks()`,
-`clamp_espn_limit()` and `merge_scoreboard_payloads()` are the pieces.
+results; `espn_date_chunks()`, `espn_request_chunks()`,
+`fetch_espn_date_chunks()`, `clamp_espn_limit()` and
+`merge_scoreboard_payloads()` are the pieces. A window's partial edge months
+are asked whole and trimmed to its days (US Eastern), and chunk requests share
+one process-wide cap of `ESPN_CHUNK_WORKERS` in flight.
 Every request goes through [`fetch_service`](#fetch_service), the chunks
 counted against the plugin that asked. Scoreboard plugins also bundle a copy
 for older cores.