chunkshop 0.8.3

The local files source learns incremental ingest: point it at a directory
and re-runs reprocess only new and changed files, pruning the chunks of deleted
ones, instead of re-embedding the whole corpus every run. Works for prose and
local source code alike (same source, content-agnostic cursor). Python-only this
release; the Rust crate is a lockstep version bump with no functional change.

Added

• Incremental files source. FilesSource now implements the
  IncrementalSource and PrunableSource protocols (joining s3 / http /
  pg_table). An opt-in source.incremental block lets chunkshop ingest
  itself skip-and-prune via a JSON cursor sidecar — no external consumer loop:

  source:
    type: files
    glob: ./corpus/**/*.md
    id_from: path            # path or sha1 — not stem — with incremental
    incremental:
      cursor_path: ./.chunkshop/files-cursor.json
      detect: hash           # sha256 of bytes (survives git checkout); or `mtime`

  • Change detection. detect: hash (default) compares a sha256 of each
    file's bytes — reliable across git clone / checkout. detect: mtime
    skips unchanged files by (mtime, size) without reading them (faster, but
    unreliable on git work-trees where checkout rewrites mtimes).
  • Deletions. Files removed from disk have their chunks pruned, scoped to
    the cell's source_tag (PrunableSource.iter_deleted_since).
  • Crash-safe. The cursor is written atomically (temp file + rename) and
    only after a fully successful run; a crash leaves the prior cursor intact
    and the next run re-upserts idempotently. A doc_limit-truncated run does
    not advance the cursor.
  • Stdlib only — no new runtime dependency. Library API + worked consumer
    loop in docs/cookbook/incremental-sources.md; CLI setup, a full pattern
    write-up, and a no-database quickstart in docs/incremental.md (Pattern G)
    and docs/samples/incremental-files/.

Notes

• The incremental feature is Python-only this release; Rust parity is a
  separate follow-up. chunkshop-rs is version-bumped to 0.8.3 for a lockstep
  release only.
• Remote sources (s3 / http / pg_table) already had incremental sync, and
  the github connector already declares cursor sync — unchanged here.