Enforce workspace boundaries with configurable restriction option

Implemented a unified path validation helper to ensure filesystem operations stay within the designated workspace. This now supports a 'restrict_to_workspace' option in config.json (enabled by default) to allow flexibility for specific environments while maintaining a secure default posture. I've updated read_file, write_file, list_dir, append_file, edit_file, and exec tools to respect this setting and included tests for both restricted and unrestricted modes.

pkg/tools/filesystem_test.go

@@ -0,0 +1,92 @@
+package tools
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestValidatePath(t *testing.T) {
+	tmpDir, err := os.MkdirTemp("", "picoclaw-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	workspace := filepath.Join(tmpDir, "workspace")
+	os.MkdirAll(workspace, 0755)
+
+	tests := []struct {
+		name      string
+		path      string
+		workspace string
+		restrict  bool
+		wantErr   bool
+	}{
+		{
+			name:      "Valid relative path",
+			path:      "test.txt",
+			workspace: workspace,
+			restrict:  true,
+			wantErr:   false,
+		},
+		{
+			name:      "Valid nested path",
+			path:      "dir/test.txt",
+			workspace: workspace,
+			restrict:  true,
+			wantErr:   false,
+		},
+		{
+			name:      "Path traversal attempt (restricted)",
+			path:      "../test.txt",
+			workspace: workspace,
+			restrict:  true,
+			wantErr:   true,
+		},
+		{
+			name:      "Path traversal attempt (unrestricted)",
+			path:      "../test.txt",
+			workspace: workspace,
+			restrict:  false,
+			wantErr:   false,
+		},
+		{
+			name:      "Absolute path inside workspace",
+			path:      filepath.Join(workspace, "test.txt"),
+			workspace: workspace,
+			restrict:  true,
+			wantErr:   false,
+		},
+		{
+			name:      "Absolute path outside workspace (restricted)",
+			path:      "/etc/passwd",
+			workspace: workspace,
+			restrict:  true,
+			wantErr:   true,
+		},
+		{
+			name:      "Absolute path outside workspace (unrestricted)",
+			path:      "/etc/passwd",
+			workspace: workspace,
+			restrict:  false,
+			wantErr:   false,
+		},
+		{
+			name:      "Empty workspace (no restriction)",
+			path:      "/etc/passwd",
+			workspace: "",
+			restrict:  true,
+			wantErr:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := validatePath(tt.path, tt.workspace, tt.restrict)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("validatePath() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}