fix(cospan-node): remove blocking_lock from diff_commits async context The structural-diff helper was calling Mutex::blocking_lock from within the async diff_commits handler, which panics under tokio. The bug pre-dated this branch but only surfaced now that v0.29.0's clippy fix unblocked the Test job in CI. Refactor: take the lock once at the top of the handler, hand the loaded import marks and an FsStore handle into the synchronous helper, and run the rest of the body lock-free.

5454     State(state): State<Arc<NodeState>>,
5555     Query(params): Query<DiffCommitsParams>,
5656 ) -> Result<Json<DiffCommitsResult>, NodeError> {
57+    // Acquire everything we need from the shared store under one async
58+    // lock acquisition; once the guard is dropped the rest of the handler
59+    // is fully synchronous and can hold non-`Send` git2 types without
60+    // making the handler future itself non-`Send`.
5761     let store = state.store.lock().await;
5862     if !store.has_git_mirror(&params.did, &params.repo) {
5963         return Err(NodeError::RefNotFound(format!(

6468     let mirror = store
6569         .open_or_init_git_mirror(&params.did, &params.repo)
6670         .map_err(|e| NodeError::Internal(format!("open mirror: {e}")))?;
71+    let import_marks = store.load_import_marks(&params.did, &params.repo);
72+    let vcs_store = store.open(&params.did, &params.repo).ok();
6773     drop(store);
6874 
6975     let from_oid = git2::Oid::from_str(&params.from)

254260     // See panproto/panproto#28 (distribute git-remote-cospan binary).
255261     let file_paths: Vec<(String, bool)> =
256262         entries.iter().map(|e| (e.path.clone(), e.binary)).collect();
257-    let structural_diffs = try_load_structural_diffs_from_vcs(
258-        &state,
259-        &params.did,
260-        &params.repo,
261-        from_oid,
262-        to_oid,
263-        &file_paths,
264-    );
263+    let structural_diffs = vcs_store.as_ref().and_then(|store| {
264+        try_load_structural_diffs_from_vcs(store, &import_marks, from_oid, to_oid, &file_paths)
265+    });
265266 
266267     let files: Vec<FileDiff> = entries
267268         .iter()

304305 ///
305306 /// Walks each commit's `SchemaTree` (panproto issue #49) into a
306307 /// `path -> FileSchemaObject` map, then diffs per-file schemas natively.
308+///
309+/// Synchronous: callers obtain `vcs_store` and `import_marks` from the
310+/// shared `NodeState.store` lock once at the top of the handler, then
311+/// pass them in here so this function does not need to await.
307312 fn try_load_structural_diffs_from_vcs(
308-    state: &Arc<NodeState>,
309-    did: &str,
310-    repo: &str,
313+    vcs_store: &panproto_core::vcs::FsStore,
314+    import_marks: &std::collections::HashMap<git2::Oid, panproto_core::vcs::ObjectId>,
311315     from_git_oid: git2::Oid,
312316     to_git_oid: git2::Oid,
313317     file_paths: &[(String, bool)],
314318 ) -> Option<std::collections::HashMap<String, serde_json::Value>> {
315319     use panproto_core::vcs::{self, FileSchemaObject, Object, Store};
316320 
317-    let store_guard = state.store.blocking_lock();
318-    let marks = store_guard.load_import_marks(did, repo);
319-    let from_pp = marks.get(&from_git_oid).copied()?;
320-    let to_pp = marks.get(&to_git_oid).copied()?;
321-    let vcs_store = store_guard.open(did, repo).ok()?;
322-    drop(store_guard);
321+    let from_pp = import_marks.get(&from_git_oid).copied()?;
322+    let to_pp = import_marks.get(&to_git_oid).copied()?;
323323 
324324     fn collect_leaves<S: Store>(
325325         store: &S,

338338         Some(out)
339339     }
340340 
341-    let from_leaves = collect_leaves(&vcs_store, &from_pp)?;
342-    let to_leaves = collect_leaves(&vcs_store, &to_pp)?;
341+    let from_leaves = collect_leaves(vcs_store, &from_pp)?;
342+    let to_leaves = collect_leaves(vcs_store, &to_pp)?;
343343 
344344     // Produce an empty schema matching the shape of `template`, used when a
345345     // file is pure-add or pure-delete (only one side has a leaf).