Tag releases (#31)

- docs: tag releases (4857f08e8aedd83922c407c1c185828ca18dee1c)
- Remove unrelated file.tex from release-tagging PR (388542498c91cb53512915432dc11fa9d9a14cdd)

AGENTS.md

@@ -195,6 +195,14 @@ Two rules about all of the above:
    per-source `stats.json` files.
 4. Prepend the release notes to `CHANGELOG.md` under a new `## vX.Y.Z (date)`
    heading. History is append-only — never rewrite earlier releases.
+5. Tag the commit where the docs and the artifacts agree, and push the tag:
+   ```bash
+   git tag -a vX.Y.Z <commit> -m "vX.Y.Z stable: <docs> documents / <tokens> tokens / <n> sources"
+   git push origin vX.Y.Z
+   ```
+   A release with no tag can only be cited by hash, and every later doc fix
+   makes that hash a worse citation than the one before it — which is how
+   `v0.2.5` ended up cited three different ways. Tag it once and cite the tag.
 
 ## Push to Hugging Face