feat: harden workspace file APIs

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/model/file.go

@@ -22,3 +22,13 @@ type ReadFileResponse struct {
 	Path    string `json:"path"`
 	Content string `json:"content"`
 }
+
+// FileInfoResponse is the API response for file stat.
+// Path is always workspace-relative; host absolute paths are never exposed.
+type FileInfoResponse struct {
+	Name    string `json:"name"`
+	Path    string `json:"path"`
+	IsDir   bool   `json:"isDir"`
+	Size    int64  `json:"size"`
+	ModTime string `json:"modTime"`
+}

internal/model/workspace.go

@@ -9,3 +9,9 @@ type CreateWorkspaceRequest struct {
 type WorkspaceResponse struct {
 	ID string `json:"id"`
 }
+
+// WorkspaceListResponse is the API response for listing workspaces.
+// Root is never exposed.
+type WorkspaceListResponse struct {
+	Workspaces []WorkspaceResponse `json:"workspaces"`
+}