fix(translator): zai thinkingFormat sends reasoning.effort object

Z.ai / GLM-5.2+ require a top-level reasoning_effort (low/high/max)
alongside thinking:{type:"enabled"} to control reasoning depth; the zai
branch previously only set thinking and dropped reasoning_effort, so every
GLM-5.x request ran at the model default (max). Gate the field behind
GLM-5.2+ (thinkingEffortSupported in capabilities.js) since older GLM
(4.x, 5.0, 5.1, 5-turbo, 5v-turbo) do not read it, and map client levels
to the exact low/high/max values z.ai accepts.

extractThinking now checks reasoning_effort/reasoning.effort before the
thinking object so a client-supplied effort is not overwritten by
thinking:{type:"enabled"} mapping to mode:auto.

Fixes #2721

tests/translator/thinking-unified.test.js

@@ -58,6 +58,18 @@ describe("extractThinking", () => {
   it("no intent → null", () => {
     expect(extractThinking({ messages: [] })).toBeNull();
   });
+  it("reasoning_effort wins over thinking:{type:enabled} (no budget)", () => {
+    expect(extractThinking({
+      thinking: { type: "enabled" },
+      reasoning_effort: "high",
+    })).toEqual({ mode: "level", level: "high" });
+  });
+  it("reasoning.effort wins over thinking:{type:enabled} (no budget)", () => {
+    expect(extractThinking({
+      thinking: { type: "enabled" },
+      reasoning: { effort: "medium" },
+    })).toEqual({ mode: "level", level: "medium" });
+  });
 });
 
 describe("applyThinking per provider format", () => {
@@ -114,6 +126,27 @@ describe("applyThinking per provider format", () => {
     expect(out.enable_thinking).toBe(false);
     expect(out.thinking).toBeUndefined();
   });
+  it.each([
+    ["high", "high"],
+    ["max", "max"],
+    ["xhigh", "max"],
+    ["low", "low"],
+    ["medium", "high"],
+    ["minimal", "low"],
+  ])("GLM-5.3 %s → reasoning_effort=%s (low|high|max only, per z.ai docs)", (input, expected) => {
+    const out = apply("openai", "glm-5.3", { reasoning_effort: input }, "glm-cn");
+    expect(out.thinking).toEqual({ type: "enabled" });
+    expect(out.reasoning_effort).toBe(expected);
+  });
+  it("GLM-5.2 also gets reasoning_effort (supported from 5.2 onward)", () => {
+    const out = apply("openai", "glm-5.2", { reasoning_effort: "low" }, "glm-cn");
+    expect(out.reasoning_effort).toBe("low");
+  });
+  it("GLM-4.7 (pre-5.2) does not get reasoning_effort — z.ai ignores it", () => {
+    const out = apply("openai", "glm-4.7", { reasoning_effort: "low" }, "glm-cn");
+    expect(out.thinking).toEqual({ type: "enabled" });
+    expect(out.reasoning_effort).toBeUndefined();
+  });
   it("Qwen on → enable_thinking + thinking_budget", () => {
     const out = apply("openai", "qwen3-max", { reasoning_effort: "medium" }, "qwen");
     expect(out.enable_thinking).toBe(true);