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>

README.md

@@ -85,7 +85,9 @@ https://git.westgate.pw/ShadowsOverWestgate/sow-docs).
 - `ci.yml` — vet, test, shellcheck, yamllint, binary smoke, and cross-build all
   targets once per pull request.
 - `build-binaries.yml` — on a `v*` tag, cross-build and upload the binaries,
-  `SHA256SUMS`, and the wrappers to the Gitea release.
+  `SHA256SUMS`, and the wrappers to the Gitea release, then delete the assets
+  of every release except the newest two — Gitea keeps them forever otherwise,
+  and every binary is reproducible from its tag.
 - `sync-wrappers.yml` — on a `main` push that touches `wrappers/`, auto-PR the
   canonical wrappers to the consumer repos in `wrappers/consumers.txt`.
   Consumer drift checks run after those PRs merge to `main`, not on the PRs