fix: Update FileDataSource to process reload triggers under lock. (#199)

Put the load under lock so only a single load is happening concurrently.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Synchronizes `LoadAll()` in `FileDataSource` with a lock to prevent
concurrent reloads from file watcher events.
> 
> - **Server SDK – File data loading**:
> - Add `_updateLock` and wrap `LoadAll()` body in `lock` to serialize
reloads and avoid concurrent loads from file watcher.
> - All versioning, parsing, and `_dataSourceUpdates.Init(...)` now
occur within the critical section in
`pkgs/sdk/server/src/Internal/DataSources/FileDataSource.cs`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
b32dc5a. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: kinyoklion

pkgs/sdk/server/src/Internal/DataSources/FileDataSource.cs

@@ -26,6 +26,7 @@ internal sealed class FileDataSource : IDataSource
         private volatile bool _started;
         private volatile bool _loadedValidData;
         private volatile int _lastVersion;
+        private object _updateLock = new object();
 
         public FileDataSource(IDataSourceUpdates dataSourceUpdates, FileDataTypes.IFileReader fileReader,
             List<string> paths, bool autoUpdate, Func<string, object> alternateParser, bool skipMissingPaths,
@@ -88,35 +89,39 @@ private void Dispose(bool disposing)
 
         private void LoadAll()
         {
-            var version = Interlocked.Increment(ref _lastVersion);
-            var flags = new Dictionary<string, ItemDescriptor>();
-            var segments = new Dictionary<string, ItemDescriptor>();
-            foreach (var path in _paths)
+            lock (_updateLock)
             {
-                try
-                {
-                    var content = _fileReader.ReadAllText(path);
-                    _logger.Debug("file data: {0}", content);
-                    var data = _parser.Parse(content, version);
-                    _dataMerger.AddToData(data, flags, segments);
-                }
-                catch (FileNotFoundException) when (_skipMissingPaths)
+                var version = Interlocked.Increment(ref _lastVersion);
+                var flags = new Dictionary<string, ItemDescriptor>();
+                var segments = new Dictionary<string, ItemDescriptor>();
+                foreach (var path in _paths)
                 {
-                    _logger.Debug("{0}: {1}", path, "File not found");
-                }
-                catch (Exception e)
-                {
-                    LogHelpers.LogException(_logger, "Failed to load " + path, e);
-                    return;
+                    try
+                    {
+                        var content = _fileReader.ReadAllText(path);
+                        _logger.Debug("file data: {0}", content);
+                        var data = _parser.Parse(content, version);
+                        _dataMerger.AddToData(data, flags, segments);
+                    }
+                    catch (FileNotFoundException) when (_skipMissingPaths)
+                    {
+                        _logger.Debug("{0}: {1}", path, "File not found");
+                    }
+                    catch (Exception e)
+                    {
+                        LogHelpers.LogException(_logger, "Failed to load " + path, e);
+                        return;
+                    }
                 }
+
+                var allData = new FullDataSet<ItemDescriptor>(
+                    ImmutableDictionary.Create<DataKind, KeyedItems<ItemDescriptor>>()
+                        .SetItem(DataModel.Features, new KeyedItems<ItemDescriptor>(flags))
+                        .SetItem(DataModel.Segments, new KeyedItems<ItemDescriptor>(segments))
+                );
+                _dataSourceUpdates.Init(allData);
+                _loadedValidData = true;
             }
-            var allData = new FullDataSet<ItemDescriptor>(
-                ImmutableDictionary.Create<DataKind, KeyedItems<ItemDescriptor>>()
-                    .SetItem(DataModel.Features, new KeyedItems<ItemDescriptor>(flags))
-                    .SetItem(DataModel.Segments, new KeyedItems<ItemDescriptor>(segments))
-            );
-            _dataSourceUpdates.Init(allData);
-            _loadedValidData = true;
         }
 
         private void TriggerReload()