v0.7.0

Added

• BlobStore::read_blobs — a batched full-frame read on the public trait.
  The default loops over read_blob; stores override it for device
  parallelism (Linux io_uring submits one ring batch, the pread store
  fans the reads across worker threads). Used by the cold-scan read-ahead.
• Page-granular cold reads. A point lookup on routed (write-cold) data fetches
  only the header page, the blob's routing region, and the one leaf page its
  descent reaches (~18 KB mean) instead of pinning the whole 512 KB frame
  (~27× less cold I/O). The routing region is built at compaction.
• Per-blob bloom filter at the tail of the routing region (read for free with
  it): cold negative lookups answer NotFound without a leaf-page read.
  No false negatives. Additive on disk (bloom_len == 0 = no bloom).
• Bounded resident routing cache: routing regions for hot blobs are held in a
  byte-bounded cache so repeat cold reads skip the routing-region read.
• Cold-scan I/O read-ahead: range scans prefetch upcoming child blobs through
  pin_scan_many → batched read_blobs, reading them at the device's natural
  queue depth instead of one serial round-trip each.

Changed

• Breaking — on-disk format. Manifest format v4 → v6 (the blob header now
  records the per-blob routing-region geometry). Older manifests are not
  migrated — the loader rejects any non-v6 manifest, so a store written by
  0.6.x cannot be opened by this release (and a v6 store cannot be opened by
  0.6.x). Pre-1.0 with no production deployments; recreate the store on upgrade.
• Compaction builds (and the read path validates) the routing region + bloom;
  structural write-path mutations de-route a blob, and write-cold blobs are
  re-routed lazily by maintenance.

Removed

• Removed the cold.idx cold-read sidecar — the in-blob routing region is now
  the sole cold-read path.
• Removed the docs/design/ working notes. Rationale for shipped features lives
  in commit messages; rationale for rejected paths (io_uring WAL rewrite, the
  two blob-fill fixes) lives in git history.