feat(minimax): add image generation provider and trim model catalog to M2.7 (#54487)

* feat(minimax): add image generation and TTS providers, trim TUI model list

Register MiniMax image-01 and speech-2.8 models as plugin providers for
the image_generate and TTS tools. Both resolve CN/global base URLs from
the configured model endpoint origin.

- Image generation: base64 response, aspect-ratio support, image-to-image
  via subject_reference, registered for minimax and minimax-portal
- TTS: speech-2.8-turbo (default) and speech-2.8-hd, hex-encoded audio,
  voice listing via get_voice API, telephony PCM support
- Add MiniMax to TTS auto-detection cascade (after ElevenLabs, before
  Microsoft) and TTS config section
- Remove MiniMax-VL-01, M2, M2.1, M2.5 and variants from TUI picker;
  keep M2.7 and M2.7-highspeed only (backend routing unchanged)

* feat(minimax): trim legacy model catalog to M2.7 only

Cherry-picked from temp/feat/minimax-trim-legacy-models (949ed28).
Removes MiniMax-VL-01, M2, M2.1, M2.5 and variants from the model
catalog, model order, modern model matchers, OAuth config, docs, and
tests. Keeps only M2.7 and M2.7-highspeed.

Conflicts resolved:
- provider-catalog.ts: removed MINIMAX_TUI_MODELS filter (no longer
  needed since source array is now M2.7-only)
- index.ts: kept image generation + speech provider registrations
  (added by this branch), moved media understanding registrations
  earlier (as intended by the cherry-picked commit)

* fix(minimax): update discovery contract test to reflect M2.7-only catalog

Cherry-picked from temp/feat/minimax-trim-legacy-models (2c750cb).

* feat(minimax): add web search provider and register in plugin entry

* fix(minimax): resolve OAuth credentials for TTS speech provider

* MiniMax: remove web search and TTS providers

* fix(minimax): throw on empty images array after generation failure

* feat(minimax): add image generation provider and trim catalog to M2.7 (#54487) (thanks @liyuan97)

---------

Co-authored-by: tars90percent <tars@minimaxi.com>
Co-authored-by: George Zhang <georgezhangtj97@gmail.com>

src/agents/tools/image-tool.helpers.ts

@@ -63,18 +63,7 @@ export function resolveProviderVisionModelFromConfig(params: {
     | { models?: Array<{ id?: string; input?: string[] }> }
     | undefined;
   const models = providerCfg?.models ?? [];
-  const preferMinimaxVl =
-    params.provider === "minimax"
-      ? models.find(
-          (m) =>
-            (m?.id ?? "").trim() === "MiniMax-VL-01" &&
-            Array.isArray(m?.input) &&
-            m.input.includes("image"),
-        )
-      : null;
-  const picked =
-    preferMinimaxVl ??
-    models.find((m) => Boolean((m?.id ?? "").trim()) && m.input?.includes("image"));
+  const picked = models.find((m) => Boolean((m?.id ?? "").trim()) && m.input?.includes("image"));
   const id = (picked?.id ?? "").trim();
   return id ? `${params.provider}/${id}` : null;
 }