Instead of setting context = events (which made repliesByParentId always
empty), query the repository for events that #e-tag our matched event
IDs with kinds NOTE, COMMENT, or REACTION. This gives buildParameters
real reply/reaction data to count.
Fixes the bug where every event in the digest email showed
'0 replies / 0 reactions'.
Added test/digest-reply-stats.test.ts that:
- Publishes reply and reaction events into a mock repository
- Calls sendFromStoredEvents with only the parent event
- Asserts that the resulting digest parameters show Replies >= 1 and
Reactions >= 1
