feat: scaffold codespace backend

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

internal/model/process.go

@@ -0,0 +1,8 @@
+package model
+
+// ProcessStatusResponse is the API response for process status.
+type ProcessStatusResponse struct {
+	WorkspaceID string `json:"workspaceId"`
+	Running     bool   `json:"running"`
+	PID         int    `json:"pid,omitempty"`
+}