refactor: expect 类型模型重构，Raw/Resolved 双层分离与断言基础设施内聚

- 重命名 ContentRules→ContentExpectations, KeyValueExpect→KeyedExpectations
- 新增 Raw/Resolved 双层模型：resolve 阶段物化为执行计划，store 持久化 Raw 快照
- HTTP body 按需读取：status/headers 失败或无 body expectation 时不读取 body
- 新增 displayValueExpectation() 解包 failure.expected 用户可读展示
- 修复 checkEarlyTimeout 独立 lte/lt 检查，修复 KeyedExpectations JSON Schema
- 新增 expect/value.ts(resolve/check/display)、keyed.ts、content.ts、headers.ts、status.ts
- 删除旧 normalize.ts/matcher.ts/validate-matcher.ts/key-value.ts
- 更新 DEVELOPMENT.md：expect 五层管线表、displayValueExpectation、1.7↔1.10 交叉引用
- 同步 13 个 main specs，归档 refactor-expect-type-model 变更（62/62 tasks）

tests/server/checker/runner/shared/duplicate-header-key.test.ts

@@ -0,0 +1,65 @@
+import { describe, expect, test } from "bun:test";
+
+import type { CheckerValidationInput } from "../../../../../src/server/checker/runner/types";
+
+import { validateDbConfig } from "../../../../../src/server/checker/runner/db/validate";
+import { validateHttpConfig } from "../../../../../src/server/checker/runner/http/validate";
+import { validateLlmConfig } from "../../../../../src/server/checker/runner/llm/validate";
+
+function input(target: Record<string, unknown>): CheckerValidationInput {
+  return { defaults: {}, targets: [target as CheckerValidationInput["targets"][number]] };
+}
+
+describe("HTTP/LLM headers reject case-insensitive duplicate keys", () => {
+  test("HTTP headers 大小写不同的重复 key 报错", () => {
+    const target = {
+      expect: { headers: { "Content-Type": "application/json", "content-type": "text/plain" } },
+      http: { url: "https://example.com" },
+      id: "dup",
+      type: "http",
+    };
+
+    const issues = validateHttpConfig(input(target));
+    expect(issues.some((i) => i.code === "duplicate-key" && i.path.includes("headers"))).toBe(true);
+  });
+
+  test("LLM headers 大小写不同的重复 key 报错", () => {
+    const target = {
+      expect: { headers: { "X-Trace": "a", "x-trace": "b" } },
+      id: "dup",
+      llm: {
+        mode: "stream",
+        model: "test-model",
+        prompt: "hello",
+        provider: "openai",
+        url: "https://example.com/v1/chat/completions",
+      },
+      type: "llm",
+    };
+
+    const issues = validateLlmConfig(input(target));
+    expect(issues.some((i) => i.code === "duplicate-key" && i.path.includes("headers"))).toBe(true);
+  });
+
+  test("HTTP headers 不同 key 不触发 duplicate-key", () => {
+    const target = {
+      expect: { headers: { Accept: "application/json", "Content-Type": "application/json" } },
+      http: { url: "https://example.com" },
+      id: "ok",
+      type: "http",
+    };
+
+    expect(validateHttpConfig(input(target)).some((i) => i.code === "duplicate-key")).toBe(false);
+  });
+
+  test("DB rows 保留大小写敏感不触发 duplicate-key", () => {
+    const target = {
+      db: { query: "SELECT 1", url: "sqlite://:memory:" },
+      expect: { rows: [{ Name: "a", name: "b" }] },
+      id: "dup-rows",
+      type: "db",
+    };
+
+    expect(validateDbConfig(input(target)).some((i) => i.code === "duplicate-key")).toBe(false);
+  });
+});