fix(minimax): Bổ sung MiniMax-M3 + cập nhật Quota Tracker coding/CN

Squash-merge PR #1631 (decolua/9router) — chỉ lấy file code + test, bỏ docs.

- feat(minimax): add MiniMax-M3 to intl + cn provider models (targetFormat claude)
- feat(minimax): add MiniMax-M3 pricing entry
- fix(minimax): translate Claude body khi content=null (M3 thinking-only)
- fix(minimax): hiển thị quota M-series bucket "general"/"MiniMax-M*" + percent-only
- test: minimax usage / model registration / pricing

Co-Authored-By: Claude <noreply@anthropic.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

tests/unit/provider-models-minimax-m3.test.js

@@ -0,0 +1,52 @@
+/**
+ * Unit tests verifying MiniMax-M3 is registered as a first-class
+ * built-in model for both the `minimax` (international) and
+ * `minimax-cn` (China) providers, with `targetFormat: "claude"`.
+ *
+ * Run: cd tests && NODE_PATH=/tmp/node_modules /tmp/node_modules/.bin/vitest run tests/unit/provider-models-minimax-m3.test.js --reporter=verbose
+ */
+
+import { describe, it, expect } from "vitest";
+import { PROVIDER_MODELS, getModelsByProviderId } from "../../open-sse/config/providerModels.js";
+
+describe("MiniMax-M3 model registration", () => {
+  it("includes MiniMax-M3 in PROVIDER_MODELS.minimax", () => {
+    const models = PROVIDER_MODELS.minimax || [];
+    const m3 = models.find((m) => m.id === "MiniMax-M3");
+    expect(m3).toBeDefined();
+    expect(m3).toMatchObject({
+      id: "MiniMax-M3",
+      name: "MiniMax M3",
+      targetFormat: "claude",
+    });
+  });
+
+  it("includes MiniMax-M3 in PROVIDER_MODELS['minimax-cn']", () => {
+    const models = PROVIDER_MODELS["minimax-cn"] || [];
+    const m3 = models.find((m) => m.id === "MiniMax-M3");
+    expect(m3).toBeDefined();
+    expect(m3).toMatchObject({
+      id: "MiniMax-M3",
+      name: "MiniMax M3",
+      targetFormat: "claude",
+    });
+  });
+
+  it("exposes MiniMax-M3 through getModelsByProviderId for both provider IDs", () => {
+    const intlModels = getModelsByProviderId("minimax");
+    const cnModels = getModelsByProviderId("minimax-cn");
+
+    expect(intlModels.some((m) => m.id === "MiniMax-M3")).toBe(true);
+    expect(cnModels.some((m) => m.id === "MiniMax-M3")).toBe(true);
+  });
+
+  it("does not regress the existing M2.7 / M2.5 / M2.1 entries", () => {
+    const intlIds = (PROVIDER_MODELS.minimax || []).map((m) => m.id);
+    const cnIds = (PROVIDER_MODELS["minimax-cn"] || []).map((m) => m.id);
+
+    for (const id of ["MiniMax-M2.7", "MiniMax-M2.5", "MiniMax-M2.1"]) {
+      expect(intlIds).toContain(id);
+      expect(cnIds).toContain(id);
+    }
+  });
+});