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/web/utils/target.test.ts

@@ -0,0 +1,32 @@
+import { describe, expect, test } from "bun:test";
+
+import type { TargetStatus } from "../../../src/shared/api";
+
+import { getTargetDisplayName } from "../../../src/web/utils/target";
+
+function makeTarget(overrides: Partial<TargetStatus> = {}): TargetStatus {
+  return {
+    currentStreak: null,
+    description: null,
+    group: "default",
+    id: "api-health",
+    interval: "30s",
+    latestCheck: null,
+    name: null,
+    recentSamples: [],
+    stats: { availability: 100, downChecks: 0, totalChecks: 0, upChecks: 0 },
+    target: "https://example.com",
+    type: "http",
+    ...overrides,
+  };
+}
+
+describe("getTargetDisplayName", () => {
+  test("name 为 null 时返回 id", () => {
+    expect(getTargetDisplayName(makeTarget())).toBe("api-health");
+  });
+
+  test("name 有值时返回 name", () => {
+    expect(getTargetDisplayName(makeTarget({ name: "我的 API" }))).toBe("我的 API");
+  });
+});