fix: restore path-traversal rejection and enable tasktool config flag

- Check original key for '/' and '\' before sanitizing in session/manager.go
  and session/tasks.go, so traversal-like keys are rejected rather than
  silently normalized by SanitizeFilename (fixes TestSave_RejectsPathTraversal)
- Add "tasktool" case to IsToolEnabled switch so tools.tasktool.enabled: false
  actually disables the tool instead of falling through to default: true

pkg/config/config.go

@@ -953,6 +953,8 @@ func (t *ToolsConfig) IsToolEnabled(name string) bool {
 		return t.WriteFile.Enabled
 	case "mcp":
 		return t.MCP.Enabled
+	case "tasktool":
+		return t.TaskTool.Enabled
 	default:
 		return true
 	}

pkg/session/manager.go

@@ -151,13 +151,19 @@ func (sm *SessionManager) Save(key string) error {
 		return nil
 	}
 
+	// Reject keys containing path separators before sanitizing, so that
+	// traversal-like inputs (e.g. "foo/bar") are never silently normalized.
+	if strings.ContainsAny(key, `/\`) {
+		return os.ErrInvalid
+	}
+
 	filename := fileutil.SanitizeFilename(key)
 
 	// filepath.IsLocal rejects empty names, "..", absolute paths, and
 	// OS-reserved device names (NUL, COM1 … on Windows).
-	// The extra checks reject "." and any directory separators so that
-	// the session file is always written directly inside sm.storage.
-	if filename == "." || !filepath.IsLocal(filename) || strings.ContainsAny(filename, `/\`) {
+	// The extra check rejects "." so that the session file is always
+	// written directly inside sm.storage.
+	if filename == "." || !filepath.IsLocal(filename) {
 		return os.ErrInvalid
 	}
 

pkg/session/tasks.go

@@ -154,9 +154,15 @@ func (tm *TaskManager) Save(key string) error {
 	if err := os.MkdirAll(tm.storage, 0o755); err != nil {
 		return err
 	}
+	// Reject keys containing path separators before sanitizing, so that
+	// traversal-like inputs (e.g. "foo/bar") are never silently normalized.
+	if strings.ContainsAny(key, "/\\") {
+		return os.ErrInvalid
+	}
+
 	filename := fileutil.SanitizeFilename(key) + "_tasks.json"
 
-	if filename == "." || !filepath.IsLocal(filename) || strings.ContainsAny(filename, "/\\") {
+	if filename == "." || !filepath.IsLocal(filename) {
 		return os.ErrInvalid
 	}