v0.2.0

Added

• lean-semantic-search-retrieval: a Corpus trait — the storage seam a later persistent store implements — with the
  in-memory inverted index as the reference implementation, and retrieve_across for fanning one anchor across a slice
  of corpora into one bounded, ranked list.
• lean-semantic-search-store: a persisted, on-disk Corpus over SQLite — a streaming, order-agnostic build with a
  query-bounded resident set and an atomic single-file publish. Store::open_fresh reuses a corpus only on a matching
  opaque corpus_token and matching schema_version/policy_version, reporting every mismatch or corruption as a
  structured CacheMiss rather than an error; set_latest/cleanup are neutral, latest-pointer-protecting,
  dry-run-by-default primitives over content-addressed corpus directories. The store records the versions and the opaque
  token but never interprets the token's contents. See docs/architecture/05-sqlite-store.md and
  docs/architecture/06-cache-lifecycle.md.

Changed

• lean-semantic-search-retrieval: bounded selection now bounds a fingerprint/statement lane and a role/binder lane
  separately and unions them, so a selective role match is not crowded out behind a fingerprint cohort.
  RETRIEVAL_POLICY_VERSION moves to lean-semantic-search.retrieval.v2. Ranking accumulates by declaration_id
  rather than a dense row index, so a non-contiguous backend can implement Corpus. See
  docs/architecture/04-persistence.md.