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

src/web/components/TargetDetailDrawer.tsx

@@ -5,6 +5,7 @@ import { DateRangePicker, Drawer, RadioGroup, Space, Tabs, Tag, Typography } fro
 
 import type { HistoryResponse, TargetMetricsResponse, TargetStatus } from "../../shared/api";
 
+import { getTargetDisplayName } from "../utils/target";
 import { subtractHours } from "../utils/time";
 import { HistoryTab } from "./HistoryTab";
 import { OverviewTab } from "./OverviewTab";
@@ -90,7 +91,7 @@ export function TargetDetailDrawer({
         target ? (
           <Space align="center" size={12}>
             <StatusDot up={!!isUp} />
-            <Typography.Text strong>{target.name}</Typography.Text>
+            <Typography.Text strong>{getTargetDisplayName(target)}</Typography.Text>
             <Tag size="small" theme="primary" variant="light-outline">
               {target.type}
             </Tag>

src/web/constants/target-table-columns.tsx

@@ -6,6 +6,7 @@ import type { TargetStatus } from "../../shared/api";
 
 import { StatusBar } from "../components/StatusBar";
 import { StatusDot } from "../components/StatusDot";
+import { getTargetDisplayName } from "../utils/target";
 import { getAvailabilityProgressColor } from "./color-threshold";
 import { statusFilter } from "./target-table-filters";
 import { availabilitySorter, latencySorter } from "./target-table-sorters";
@@ -22,6 +23,7 @@ export function createTargetTableColumns(checkerTypes: string[]): Array<PrimaryT
       width: 60,
     },
     {
+      cell: ({ row }: PrimaryTableCellParams<TargetStatus>) => getTargetDisplayName(row),
       colKey: "name",
       ellipsis: true,
       title: "名称",

src/web/utils/target.ts

@@ -0,0 +1,5 @@
+import type { TargetStatus } from "../../shared/api";
+
+export function getTargetDisplayName(target: TargetStatus): string {
+  return target.name ?? target.id;
+}