Documentation-only release. No behavior changes.

- Samples README rewritten to cover every worked-example sub-sample
  (bakeoff-ntsb, sales-crm, embedder-byo, incremental-pg-table,
  inline-mode) with links to each sub-README, plus every recipe YAML.
- README badges modernized — dynamic shields.io PyPI + crates.io
  version badges replace the static "v0.2.0 / v0.1.0 MVP" placeholders.
- NEW docs/storage-model.md — explains the original_content /
  embedded_content / embedding triple, when they diverge per chunker,
  and how to query each.
- docs/chunkers.md gained an oversize-behavior table — documents
  current per-chunker behavior (the if_oversize FIX is queued for 0.3.2).
- docs/extractors.md gained a "where chunk metadata comes from" section
  pointing users at pg_table.metadata_columns for source-side metadata.
- docs/architecture.md diagrams fixed — component map redrawn so Sink
  is visually downstream of providers; sequenceDiagram had unsupported
  <br/> tags in message bodies that broke the GitHub render.
- README crates.io link 404 fixed (chunkshop → chunkshop-rs).

Tests: 159 passed, 14 skipped.