FileRW: Loeschen ueber den Dateiverlauf umkehrbar, ohne Freigabe; Ordner und Unaufhebbares bleiben beim Menschen (#195)

Der Dateiverlauf (#719) haelt die Vorfassung jeder geloeschten Datei - ein
eigener Papierkorb waere doppelt. delete einer Datei, die der Verlauf aufhebt,
laeuft ohne Freigabe; Ordner nur mit recursive:true (delete_folder, Freigabe);
zu grosse Dateien oder Verlauf aus (delete_unkept, Freigabe); die Wurzel nie.
Neue Aktionen deleted und restore mit voller Pfad-/Endungspruefung.
IAgentTool.StagingAktion bekommt eine Ueberladung mit Kontext.

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

src/ClawdDotNet.Core/Engine/AgentEngine.cs

@@ -1655,7 +1655,7 @@ public sealed class AgentEngine : IAgentMessageRouter, Staging.IFrozenCallExecut
             if (_stagingGate is not null)
             {
                 // #641: Die Rechte stehen in der Werkzeugkonfiguration des Agenten.
-                var operation = tool.StagingAktion(input) ?? Staging.StagingGate.ExtractAction(arguments);
+                var operation = tool.StagingAktion(input, context) ?? Staging.StagingGate.ExtractAction(arguments);
                 var intercept = await _stagingGate.InterceptAsync(
                     agentConfig.AgentId, instanceId, runId, toolName, arguments, ct,
                     operation,

src/ClawdDotNet.Core/Files/FileHistory.cs

@@ -107,6 +107,24 @@ public sealed class FileHistory
     public bool Covers(string fullPath)
         => !IsInside(Path.GetFullPath(fullPath), Path.Combine(_agentsDirectory, FolderName));
 
+    /// <summary>
+    /// #195: Whether a delete of this file can be undone — the history is on, covers the file
+    /// and keeps content of its size. Only then is deleting it no irreversible act.
+    /// </summary>
+    public bool CanKeep(string fullPath)
+    {
+        fullPath = Path.GetFullPath(fullPath);
+        return Enabled && Covers(fullPath) && File.Exists(fullPath)
+               && new FileInfo(fullPath).Length <= (long)_settings().MaxObjectMegabytes * 1024 * 1024;
+    }
+
+    /// <summary>#195: Whether the content of a version is still kept.</summary>
+    public bool CanKeepContent(string? hash)
+        => !string.IsNullOrWhiteSpace(hash) && hash.Length == 64 && hash.All(Uri.IsHexDigit) && File.Exists(ObjectPath(hash.ToLowerInvariant()));
+
+    /// <summary>#195: How long a deleted file's content stays restorable.</summary>
+    public int RetentionDays => Math.Max(1, _settings().RetentionDays);
+
     // ─── Recording ───
 
     /// <summary>Keeps the version the file has now, before a tool changes it.</summary>

src/ClawdDotNet.Core/Staging/StagingPolicy.cs

@@ -58,6 +58,9 @@ public sealed class StagingPolicy
             ["Database.truncate"] = StagingDecision.Approve,
 
             ["FileRW.delete"] = StagingDecision.Approve,
+            // #195: FileRW names these itself — a folder at once, or a file the history cannot keep.
+            ["FileRW.delete_folder"] = StagingDecision.Approve,
+            ["FileRW.delete_unkept"] = StagingDecision.Approve,
             ["FTP.upload"] = StagingDecision.Approve,
             ["FTP.delete"] = StagingDecision.Approve,
 

src/ClawdDotNet.Core/Tools/IAgentTool.cs

@@ -77,6 +77,13 @@ public interface IAgentTool
     /// </summary>
     string? StagingAktion(JsonElement input) => null;
 
+    /// <summary>
+    /// #195: The staging key with the call's context — for a key that depends on what the call
+    /// meets (FileRW: a file the history keeps, a folder, a file too large to keep). Default:
+    /// <see cref="StagingAktion(JsonElement)"/>.
+    /// </summary>
+    string? StagingAktion(JsonElement input, AgentToolContext context) => StagingAktion(input);
+
     /// <summary>
     /// Die Operationen, die sich in der Werkzeugkonfiguration eines Agenten erlauben oder
     /// verbieten lassen (#641) - dieselben Schluessel, die <see cref="StagingAktion"/> bzw. das