AGENTS.md: fetch PR refs with noop negotiation

The Hub fails have/ack negotiation for some refs/pr/N
(fatal: expected 'acknowledgments'); noop skips it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

AGENTS.md

@@ -230,10 +230,16 @@ Opened this way the PR starts in **draft** — publish it from the web UI.
 Pick up an existing PR (42 here):
 
 ```bash
-git fetch origin refs/pr/42:pr/42 && git checkout pr/42
+GIT_LFS_SKIP_SMUDGE=1 git -c fetch.negotiationAlgorithm=noop fetch origin refs/pr/42:pr/42
+git checkout pr/42
 git push origin pr/42:refs/pr/42
 ```
 
+The `noop` negotiation is needed: for some refs the Hub fails the have/ack
+exchange (`fatal: expected 'acknowledgments'`), and skipping it makes the server
+send the full history instead. `GIT_LFS_SKIP_SMUDGE=1` keeps it to pointers;
+pull a single blob with `git lfs pull --include <path>`.
+
 `repo_type='dataset'` is required on every `huggingface_hub` call — this is a
 dataset repo, not a model. Push straight to `main` only when cutting a release.