fix(models): support minimax-portal coding plan vlm routing for image tool (openclaw#33953)

Verified:
- pnpm install --frozen-lockfile
- pnpm build
- pnpm check
- pnpm test:macmini

Co-authored-by: tars90percent <252094836+tars90percent@users.noreply.github.com>

src/agents/minimax-vlm.ts

@@ -6,6 +6,14 @@ type MinimaxBaseResp = {
   status_msg?: string;
 };
 
+export function isMinimaxVlmProvider(provider: string): boolean {
+  return provider === "minimax" || provider === "minimax-portal";
+}
+
+export function isMinimaxVlmModel(provider: string, modelId: string): boolean {
+  return isMinimaxVlmProvider(provider) && modelId.trim() === "MiniMax-VL-01";
+}
+
 function coerceApiHost(params: {
   apiHost?: string;
   modelBaseUrl?: string;