Deduplicate the postHeights query iteration into a shared generator,
extract shared pagination parsing/enrichment, and extract the idempotent
create-if-missing write pattern. Reduces CRAP for the changed post-height
code to <=6 and removes duplicated parse/attach logic across the post list
use cases. Add property tests covering the postHeight key round-trip and
ordering invariants for both the DB and indexer, exposed via a separate
'property' command.
By refactorer.
Adds a postHeights LevelDB store written by the indexer and used by
psf-memo-db to paginate recent posts and posts-by-address without full
scans. Includes unit tests and Gherkin acceptance pipelines for both
psf-memo-indexer and psf-memo-db.
By coder.