If the index-based lookup fails (shard fetch silently failed, stale
index state, etc.), try fetching the activity detail file directly from
each user shard's _merged/activities/ directory. This makes private
activities and newly-synced activities accessible even when the index
resolution fails.
Also add console.error logging when shards fail in resolveShards to
help diagnose root causes.
Davide Scaini
2ebfc7046d