FileRW: Dateiaktion ohne path abweisen, Hostpfad nicht in Fehlermeldungen

Testinstanz 2026-10-02: write mit destinationPath statt path loeste auf die
Wurzel des Arbeitsbereichs auf; die Ausnahme nannte den absoluten Ordner.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ClawdDotNet.Tools.FileRW/FileRWTool.cs

@@ -149,6 +149,9 @@ public sealed class FileRWTool : IAgentTool, IToolStateProbe
             return ToolResult.Fail($"Access denied: Action '{action}' is not allowed in workspace '{area.Name}' for this agent.");
         }
 
+        if (MissingPath(action, input) is { } missing)
+            return ToolResult.Fail(missing);
+
         // A workspace with a member list comes into being when it is first used.
         if (!area.IsPersonal && area.Name != WorkspaceLayout.Shared)
             Directory.CreateDirectory(rootPath);
@@ -177,10 +180,26 @@ public sealed class FileRWTool : IAgentTool, IToolStateProbe
         catch (Exception ex)
         {
             context.Logger.LogError(ex, "Error during FileRW action {Action}", action);
-            return ToolResult.Fail($"Error: {ex.Message}");
+            // The host's folder layout is none of the model's business — the workspace name says enough.
+            return ToolResult.Fail($"Error: {ex.Message.Replace(rootPath, $"<{area.Name}>", StringComparison.Ordinal)}");
         }
     }
 
+    /// <summary>
+    /// Actions on one file need its path. Without one, the path resolved to the workspace root:
+    /// a write then tried to move its temp file onto the folder itself (test instance, 2026-10-02,
+    /// a model that sent <c>destinationPath</c> instead of <c>path</c>).
+    /// </summary>
+    internal static string? MissingPath(string action, JsonElement input)
+    {
+        if (action is not ("read" or "write" or "append" or "delete" or "copy") || !string.IsNullOrWhiteSpace(RelativerPfad(input)))
+            return null;
+        var hint = action != "copy" && input.ValueKind == JsonValueKind.Object && input.TryGetProperty("destinationPath", out _)
+            ? " 'destinationPath' belongs to copy only — name the file in 'path'."
+            : "";
+        return $"'path' is required for {action}.{hint}";
+    }
+
     /// <summary>
     /// #579: Rechte und Pfad pruefen, bevor ein Aufruf in die Freigabeliste kommt. Dieselben
     /// Pruefungen wie in <see cref="ExecuteAsync"/>, ohne etwas anzufassen.
@@ -203,6 +222,9 @@ public sealed class FileRWTool : IAgentTool, IToolStateProbe
         if (!IsActionAllowed(action, area))
             return $"Access denied: Action '{action}' is not allowed in workspace '{area.Name}' for this agent.";
 
+        if (MissingPath(action, input) is { } missing)
+            return missing;
+
         if (action != "delete" || string.IsNullOrWhiteSpace(area.Root))
             return null;