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>

AssistentSqliteBootstrap.cs

@@ -35,14 +35,7 @@ internal static class AssistentSqliteBootstrap
         {
             return;
         }
-        string[] relPaths =
-        [
-            Path.Combine("runtimes", "linux-x64", "native", "libe_sqlite3.so"),
-            Path.Combine("runtimes", "linux-x64", "native", "e_sqlite3.so"),
-            "libe_sqlite3.so",
-            "e_sqlite3.so",
-        ];
-        foreach (string rel in relPaths)
+        foreach (string rel in CandidatePaths())
         {
             string path = Path.Combine(extDir, rel);
             if (!File.Exists(path))
@@ -51,7 +44,8 @@ internal static class AssistentSqliteBootstrap
             }
             try
             {
-                NativeLibrary.Load(path);
+                IntPtr handle = NativeLibrary.Load(path);
+                RegisterResolver(handle);
                 return;
             }
             catch (Exception ex)
@@ -60,4 +54,45 @@ internal static class AssistentSqliteBootstrap
             }
         }
     }
+
+    /// <summary>Native e_sqlite3 locations for the current OS / arch, most specific first.</summary>
+    static string[] CandidatePaths()
+    {
+        string arch = RuntimeInformation.ProcessArchitecture switch
+        {
+            Architecture.Arm64 => "arm64",
+            Architecture.X86 => "x86",
+            Architecture.Arm => "arm",
+            _ => "x64",
+        };
+        if (OperatingSystem.IsWindows())
+        {
+            return [Path.Combine("runtimes", $"win-{arch}", "native", "e_sqlite3.dll"), "e_sqlite3.dll"];
+        }
+        if (OperatingSystem.IsMacOS())
+        {
+            return [Path.Combine("runtimes", $"osx-{arch}", "native", "libe_sqlite3.dylib"), "libe_sqlite3.dylib"];
+        }
+        return
+        [
+            Path.Combine("runtimes", $"linux-{arch}", "native", "libe_sqlite3.so"),
+            Path.Combine("runtimes", $"linux-{arch}", "native", "e_sqlite3.so"),
+            "libe_sqlite3.so",
+            "e_sqlite3.so",
+        ];
+    }
+
+    /// <summary>The provider's [DllImport("e_sqlite3")] would otherwise probe the host dir, not the extension dir.</summary>
+    static void RegisterResolver(IntPtr handle)
+    {
+        try
+        {
+            NativeLibrary.SetDllImportResolver(typeof(SQLite3Provider_e_sqlite3).Assembly,
+                (name, _, _) => name.Contains("e_sqlite3", StringComparison.OrdinalIgnoreCase) ? handle : IntPtr.Zero);
+        }
+        catch (InvalidOperationException)
+        {
+            // A resolver is already set for this assembly — the preloaded handle still helps on Windows.
+        }
+    }
 }