Add store card

[dacorvo]

A pushed store lands on the Hub as a bare repo — no card, no tags, nothing saying what it is. This makes every published store carry a self-describing dataset card, created and kept current by funes push itself.

What changes

• card::plan decides, push executes. No README on the remote → write the full generated card: frontmatter (tags, size band), what a funes store is, a recall example naming the store, and a marker-delimited stats block (chunks, embedding model, last update). Markers present → rewrite only that block. A hand-written card is never touched.
• Zero extra commits. The card rides the commit that's already happening: one more operation in the first-publish commit, an extra file through hf_dataset::append's guarded commit on later pushes — atomic with the data, re-attached on conflict retries.
• Root stores only. The root README describes the whole repo, and only a root store is the repo; a store under a prefix never touches it.
• Fail-safe. If the remote README can't be read it can't be classified, so the card is skipped with a note — never clobbered, and the push is unaffected.
• Discovery. The funes tag makes every shared store recognizable and browsable on the Hub; agent-memory names the category.

Testing

• Unit: the ownership rules (create / refresh-markers-only / hands-off, malformed markers), size bands, and the push-side decision wiring.
• New gated live e2e (push_card, against a throwaway root repo): the card is created on first publish, its stats refresh on append, and a hand-written README survives further pushes byte-identical.
• The gated round-trip (prefixed store) now asserts the repo-root README is never touched.

Docs: the README's Hub section and docs/automation.md each gain the three-line version of the above.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR makes funes push publish and maintain a Hugging Face dataset card (README.md) for root stores, so pushed stores are self-describing and discoverable on the Hub (via the funes tag), while never modifying hand-written cards.

Changes:

• Add card module with planning logic to create/refresh only a marker-delimited stats region, leaving hand-written READMEs untouched.
• Wire card planning/execution into push (first publish writes README in the initial commit; append refreshes README via hf_dataset::append extra files in the same guarded commit).
• Add gated live e2e coverage for card behavior and extend round-trip push test to assert prefixed pushes never touch repo-root README; update docs.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/push_round_trip.rs	Snapshots repo-root README and asserts prefixed pushes never modify it.
tests/push_card.rs	New gated live e2e validating card creation, refresh, and hands-off behavior after manual edits.
src/push.rs	Integrates card planning into push flow and attaches README updates to commits.
src/lib.rs	Exposes new card module.
src/hf_dataset.rs	Allows appends to carry extra files (e.g., README) in the same guarded commit; adds fetch_readme.
src/card.rs	New dataset-card generation and marker-only refresh planner.
README.md	Documents dataset card behavior on first publish and subsequent pushes.
docs/automation.md	Documents that the card is created/refreshed in the same commit as pushed data.

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