docs: CHANGELOG (Keep a Changelog) + Docs-Seite

CHANGELOG.md

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+# Changelog
+
+All notable changes to **sdata** are documented here. The format is based on
+[Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project adheres to
+[Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+A large, strictly **additive** increment: a content/integrity foundation under all
+data containers (`Blob`), a much broader `DataFrame` serialization portfolio, and
+native, format-agnostic metadata embedding for images. Core dependencies remain
+`numpy`, `pandas`, `suuid`; every new backend stays optional with a pure-Python path.
+
+### Added
+
+- **Native image metadata (RFC 0005).** New pure-Python, Pillow-free module
+  `sdata.imagemeta` embeds/reads sdata metadata **natively** into six containers with
+  one API (`detect_format`/`embed`/`extract`/`supported_formats`): **PNG** (`iTXt`),
+  **JPEG** (`APP1`), **JPEG 2000** (`uuid` box), **GIF** (comment extension),
+  **WebP** (`sdAT` chunk) and **TIFF** (private IFD tag, original bytes untouched).
+  `Image` gains a uniform `save`/`from_file` flow, `embedded_metadata()`, and a
+  lossless `<file>.meta.json` **sidecar fallback** for formats without a native
+  carrier (e.g. BMP), controllable via `save(sidecar=True|False|None)`.
+- **`Blob` as the content/integrity/provenance foundation (RFC 0003).** Hardened
+  `Blob` with `sha256`/`sha1`/`md5`, `size`, `verify()`/`update_checksum()`, a lazy
+  `content_bytes` cache, `exists()`, `write(uri)`/`open()` (fsspec), standard-vocabulary
+  provenance metadata (`dcat:mediaType`, `dcterms:*`, `schema:sha256`) and
+  mime/creation-date autofill. `FileReference` and `Image` now build on `Blob`.
+- **Shared integrity mixin (RFC 0004, Option B).** `sdata.sclass.content.ContentIntegrityMixin`
+  provides the hash/`verify`/`size` layer to both `Blob` and `DataFrame` via a
+  `content_bytes` hook (no inheritance between them).
+- **`DataFrame.as_blob(fmt)` (RFC 0004, Option C).** Render a table as a standalone
+  `Blob` in a chosen format (`parquet`/`csv`/`arrow`/`feather`) — composition that
+  grants hash/`verify`/`size`/`write`/`open` without changing the base class.
+- **`DataFrame` serialization portfolio.** Native per-column field metadata in
+  **Arrow/Feather** (`to_arrow`/`from_arrow`/`to_feather`/`from_feather`), a
+  Frictionless **Data Package** bundle (`to_datapackage`/`from_datapackage`, `.zip`),
+  and **HDF5** I/O (`to_hdf`/`from_hdf`, optional `sdata[hdf]`, RFC 0002).
+- **RFCs.** 0002 (HDF5), 0003 (Blob foundation), 0004 (DataFrame vs. Blob),
+  0005 (native image metadata); MkDocs nav, API reference and usage guides extended.
+
+### Changed
+
+- `DataFrame.content_bytes` hashes the **data only** (plain Parquet), so storing the
+  checksum in the metadata does not change the hash (no self-reference).
+- Documentation reorganized around the full DataFrame serialization portfolio and the
+  image-metadata workflow (new `usage/image-metadata.md`).
+
+### Notes
+
+- 100 % line coverage maintained; `mkdocs build --strict` green. `sdata.imagemeta` is
+  measured (100 %) via synthetic, Pillow-free tests, so coverage holds even without
+  Pillow installed.
+
+## [1.2.0] - 2026-06-26
+
+- **Machine-readable metadata backbone.** Typed dtype registry, a registered JSON-LD
+  `@context` (vocab/units/BFO), `to_jsonld`/`to_rdf`/`to_turtle` with `<sname>.meta.jsonld`
+  sidecars, declarative `MetadataSchema`/`TableSchema` validation, an interactive
+  Jupyter layer (`_repr_html_`, attribute autocomplete) and signed metadata as W3C
+  **Verifiable Credentials** over the pure-Python EdDSA stack (`sdata.did`).
+- **Self-describing `DataFrame` container** with per-column metadata and Parquet/CSV/
+  dict/JSON-LD serialization, superseding the deprecated `Data` class.
+- **Docs & packaging.** MkDocs Material + mkdocstrings documentation site; core
+  dependencies reduced to `numpy`/`pandas`/`suuid` (stdlib `zoneinfo`); warning-free
+  test suite.
+
+[Unreleased]: https://github.com/lepy/sdata/compare/v1.2.0...HEAD
+[1.2.0]: https://github.com/lepy/sdata/releases/tag/v1.2.0

docs/changelog.md

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+--8<-- "CHANGELOG.md"

mkdocs.yml

@@ -73,3 +73,4 @@ nav:
       - "0004 — DataFrame and Blob": rfc/0004-dataframe-and-blob.md
       - "0005 — Native image metadata": rfc/0005-native-image-metadata.md
   - Releasing: releasing.md
+  - Changelog: changelog.md