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>

test/test_on_demand_live_and_restore.py

@@ -120,8 +120,10 @@ class TestARestoreWithNothingToResume:
     def test_it_is_reported_as_an_error(self, restored):
         assert restored.on_demand_status == 'error'
         assert restored.on_demand_last_error == 'restore-failed'
-        published = restored.cache_manager.set.call_args_list[-1]
-        assert published.args[0] == 'display_on_demand_state'
+        # The last on-demand state write, not the last write of any key: the
+        # font-usage publisher thread writes its own key at its own pace.
+        published = [c for c in restored.cache_manager.set.call_args_list
+                     if c.args and c.args[0] == 'display_on_demand_state'][-1]
         assert published.args[1]['status'] == 'error'
         assert published.args[1]['error'] == 'restore-failed'