refactor: 统一 target name/description 可空语义，前端展示 fallback 到 id

- schema: name/description 允许省略或显式 null，TypeBox Union([Null, String])
- 类型: RawTargetConfig/ResolvedTargetBase/子类型/StoredTarget/TargetStatus name 改为 string | null
- checker resolve: name: t.name ?? null，不再 fallback 到 id
- 语义校验: 拒绝空字符串和纯空白 name
- SQLite: targets.name 列改为可空 TEXT
- 前端: 新增 getTargetDisplayName(target) 展示 name ?? id
- 测试: 覆盖 name/description null 全场景，查找改为按 id
- 文档: 更新 README/DEVELOPMENT 和 6 个 openspec specs

tests/server/checker/config-loader.test.ts

@@ -234,7 +234,7 @@ targets:
     expect(cmd.cmd.maxOutputBytes).toBe(10485760);
   });
 
-  test("name 缺省时 fallback 到 id", async () => {
+  test("name 缺省时保留为 null", async () => {
     const configPath = join(tempDir, "name-fallback.yaml");
     await writeFile(
       configPath,
@@ -249,7 +249,105 @@ targets:
     const config = await loadConfig(configPath);
     const target = config.targets[0]!;
     expect(target.id).toBe("api-health");
-    expect(target.name).toBe("api-health");
+    expect(target.name).toBeNull();
+  });
+
+  test("name 显式 null 保留为 null", async () => {
+    const configPath = join(tempDir, "name-explicit-null.yaml");
+    await writeFile(
+      configPath,
+      `targets:
+  - id: "api-health"
+    name: null
+    type: http
+    http:
+      url: "http://example.com"
+`,
+    );
+
+    const config = await loadConfig(configPath);
+    expect(config.targets[0]!.name).toBeNull();
+  });
+
+  test("name YAML 空值保留为 null", async () => {
+    const configPath = join(tempDir, "name-yaml-null.yaml");
+    await writeFile(
+      configPath,
+      `targets:
+  - id: "api-health"
+    name:
+    type: http
+    http:
+      url: "http://example.com"
+`,
+    );
+
+    const config = await loadConfig(configPath);
+    expect(config.targets[0]!.name).toBeNull();
+  });
+
+  test("name 为空字符串抛出错误", async () => {
+    const configPath = join(tempDir, "empty-name.yaml");
+    await writeFile(
+      configPath,
+      `targets:
+  - id: "api-health"
+    name: ""
+    type: http
+    http:
+      url: "http://example.com"
+`,
+    );
+    // eslint-disable-next-line @typescript-eslint/await-thenable
+    await expect(loadConfig(configPath)).rejects.toThrow("name 不能为空白");
+  });
+
+  test("name 仅包含空白字符抛出错误", async () => {
+    const configPath = join(tempDir, "whitespace-name.yaml");
+    await writeFile(
+      configPath,
+      `targets:
+  - id: "api-health"
+    name: "   "
+    type: http
+    http:
+      url: "http://example.com"
+`,
+    );
+    // eslint-disable-next-line @typescript-eslint/await-thenable
+    await expect(loadConfig(configPath)).rejects.toThrow("name 不能为空白");
+  });
+
+  test("description 显式 null 保留为 null", async () => {
+    const configPath = join(tempDir, "description-null.yaml");
+    await writeFile(
+      configPath,
+      `targets:
+  - id: "api-health"
+    description: null
+    type: http
+    http:
+      url: "http://example.com"
+`,
+    );
+    const config = await loadConfig(configPath);
+    expect(config.targets[0]!.description).toBeNull();
+  });
+
+  test("description YAML 空值保留为 null", async () => {
+    const configPath = join(tempDir, "description-yaml-null.yaml");
+    await writeFile(
+      configPath,
+      `targets:
+  - id: "api-health"
+    description:
+    type: http
+    http:
+      url: "http://example.com"
+`,
+    );
+    const config = await loadConfig(configPath);
+    expect(config.targets[0]!.description).toBeNull();
   });
 
   test("name 支持变量替换且不要求唯一", async () => {