MANUAL RUN: codeSplitter tags on a hosted (Cloudflare Artifacts) repo #892

Follow-up to #879. Tags are listed, made and deleted over git smart HTTP (apps/codesplitter/src/tags.ts): the git-upload-pack advert with a read token to list, and a git-receive-pack with an empty pack (a delete sends none) to write. Tests cover the desktop's bare repos behind git http-backend. Nobody has tried it against Cloudflare Artifacts yet.

On a deployed codeSplitter, on a repo you own with a commit or two:

1. Open the git map, pick a dot in the commit graph, type v0.1 and press Enter. The dot gets a tag.
2. git ls-remote --tags <the repo's clone URL> shows refs/tags/v0.1 on that commit.
3. Delete it with the × on its chip in the bar. It's gone from the graph and from ls-remote.

If the list comes back empty while ls-remote shows tags, Artifacts may be answering the upload-pack advert as protocol v2 only, and remoteRefs in src/git.ts would need to send Git-Protocol: version=2 and ask with ls-refs. If the make fails, the error toast has the remote's reason.