Add OpenRouter chat provider; fix Windows load errors (0.17.0).

- OpenRouter as an alternative chat provider: server-side API key
  (settings.json or OPENROUTER_API_KEY), model list with vision marks and
  filter, SSE streaming, images as data URLs. Memory embeddings stay on Ollama;
  park/warm LLM are no-ops for the remote provider.
- AssistentSaveKnowledgeAttach: JArray param is not supported by SwarmUI API
  reflection and aborted registration of every later API call; use string[].
- SQLite bootstrap: preload native e_sqlite3 for the current OS/arch
  (win/osx/linux) and resolve DllImport to it.
- settings.json: shared-read + atomic write with retry to avoid Windows
  sharing violations.
- csproj: fix MSB4012 in the native SQLite copy target.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

AssistentConfig.cs

@@ -117,7 +117,10 @@ public sealed class AssistentConfig
         }
         try
         {
-            return JObject.Parse(File.ReadAllText(path, Encoding.UTF8));
+            // Share read/write/delete: Windows otherwise fails a concurrent SaveSettings with a sharing violation.
+            using FileStream fs = new(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
+            using StreamReader reader = new(fs, Encoding.UTF8);
+            return JObject.Parse(reader.ReadToEnd());
         }
         catch (Exception ex)
         {
@@ -1671,7 +1674,32 @@ public sealed class AssistentConfig
             Directory.CreateDirectory(_overlayRoot);
             string path = Path.Combine(_overlayRoot, "settings.json");
             JObject merged = DeepMerge(LoadSettings(), settings ?? new JObject());
-            File.WriteAllText(path, merged.ToString(Newtonsoft.Json.Formatting.Indented), Encoding.UTF8);
+            WriteFileAtomic(path, merged.ToString(Newtonsoft.Json.Formatting.Indented));
+        }
+    }
+
+    /// <summary>Temp file + rename, retried briefly: readers never see a half-written file and a
+    /// transient lock (antivirus, editor, parallel read) does not fail the API call.</summary>
+    static void WriteFileAtomic(string path, string text)
+    {
+        string tmp = $"{path}.{Guid.NewGuid():N}.tmp";
+        File.WriteAllText(tmp, text, Encoding.UTF8);
+        for (int attempt = 0; ; attempt++)
+        {
+            try
+            {
+                File.Move(tmp, path, overwrite: true);
+                return;
+            }
+            catch (IOException) when (attempt < 10)
+            {
+                System.Threading.Thread.Sleep(25 * (attempt + 1));
+            }
+            catch
+            {
+                try { File.Delete(tmp); } catch { }
+                throw;
+            }
         }
     }