Rewrite digest.agent to be fully autonomous — it uses journal_tail
to discover what needs digesting and generates digests during its
run. No more pre-populated {{CONTENT}}/{{LEVEL}} placeholders.
Extend journal_tail with level parameter (0=journal, 1=daily,
2=weekly, 3=monthly) and keys_only mode. Also include node keys
in full output for better agent context.
Remove stale format:"neighborhood" case from memory_query.
Co-Authored-By: Proof of Concept <poc@bcachefs.org>
568ce417fc