feat(ci): prune release assets outside the newest two tags (#52) (#70)

Closes #52.

Adds `scripts/prune-release-assets.sh` and a best-effort step at the end of `build-binaries.yml`.

- Lists every release page, sorts by creation date, skips the newest two published releases, deletes the rest's attachments via `DELETE /releases/{id}/assets/{asset_id}`.
- Drafts never consume a keep slot, so a draft cannot strip the newest real release.
- Releases, tags, source archives and release notes are never touched.
- Nothing is excluded: SHA256SUMS and the wrappers go with the binaries. Checksums are only meaningful next to the files they cover, and the consumer drift-check reads the wrappers from the latest release, which stays complete.
- Failures warn and the step has `continue-on-error: true` — a stale asset is cheaper than a blocked publish.

`tests/prune-release-assets.sh` drives the script with a stub `curl`: keep window, out-of-order responses, drafts, no non-asset DELETE, short-page pagination stop, and both failure paths. Wired into `make check`.

v0.2.0 still needs its 9 assets cleared by hand in the web UI, as the issue notes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #70

Co-authored-by: vickydotbat <vickydotbat@tutamail.com>

.gitea/workflows/build-binaries.yml

@@ -65,3 +65,17 @@ jobs:
                 "${api}/releases/${id}/assets?name=$(basename "$f")"
             done
           '
+
+      # Gitea has no asset retention (#52): without this every tag keeps its
+      # ~57 MB binary set forever. Best-effort — a stale asset is cheaper than
+      # a blocked publish, so a failure here never fails the release.
+      - name: Prune assets of older releases
+        continue-on-error: true
+        env:
+          TOKEN: ${{ secrets.GITEA_TOKEN }}
+          REPO: ${{ github.repository }}
+          SERVER: ${{ github.server_url }}
+        run: |
+          nix develop --command bash -c '
+            API="${SERVER}/api/v1/repos/${REPO}" scripts/prune-release-assets.sh
+          '