perf(sync): hash-set membership check in get_sync_status

The deletion-detection loop in `get_sync_status` scanned `local_files`
linearly for every tracked path in `sync_state.files`, making the cost
quadratic in the file count.  The earlier "pending change" loop just
above already does the inverse direction via `sync_state.files.get`
(O(1)).  Build a `HashSet<&str>` of local paths once and check it
the same way to make the function O(n).

This is called by the GUI status indicator, so the win shows up as
soon as a workspace tracks more than a handful of files.

crates/onyx-core/src/sync.rs

@@ -914,9 +914,15 @@ pub fn get_sync_status(workspace_path: &Path) -> Result<SyncStatusInfo> {
         }
     }
 
-    // Count files in base that are now missing locally (deleted)
+    // Count files in base that are now missing locally (deleted).
+    // Build a set of local paths once so the membership check is O(1) per
+    // tracked file instead of scanning local_files linearly each time.
+    let local_paths: std::collections::HashSet<&str> = local_files
+        .iter()
+        .map(|f| f.path.as_str())
+        .collect();
     for path in sync_state.files.keys() {
-        if !local_files.iter().any(|f| f.path == *path) {
+        if !local_paths.contains(path.as_str()) {
             pending_changes += 1;
         }
     }