v0.1.0

Added

• codemeta-drift <checkout> [--ref REF] [--json] lists where CodeMeta's context,
  definitions, property table, examples, crosswalks and crosswalk.csv disagree. Each check
  has a stable code. A malformed input file exits 2, so CI doesn't mistake it for drift.
• --json prints one versioned document holding the findings, and --version prints the installed version.
• --ref reads any tag, branch or commit through one git cat-file call, about as fast as
  reading the working tree.
• The mapping export format: a JSON Schema for mapping-<codemeta-tag>.json, which says where
  each CodeMeta term sits in six metadata formats, and the export for CodeMeta 3.1.
• codemeta-drift export [checkout] --tag TAG [--out FILE] writes the export from the tag's
  commit. Rows read the crosswalk cell when it is a path, and come from a curated file with a
  reason when it is prose, empty or wrong. A cell with neither is listed and the command exits 1,
  as is a curated row whose cell has changed, and two terms whose paths overlap.
• export --schemas DIR checks every path against the format's own JSON Schema (CFF 1.2.0,
  pyproject.toml, package.json, Cargo.toml) and reports PATH_NOT_IN_SCHEMA.
• Test fixtures: the files the checks read from CodeMeta 3.1 and 4.0, and the output for each,
  and the JSON Schemas of four formats. tests/fixtures/3.1.sha256 ties the 3.1 files to the
  tag's commit.