feat(flow): 流程图入口/失败提示/指派预览/线级停发闭环/配置分层/选人宿主

- 修复办理页「查看流程图」双 hash URL：改 router.resolve + toAppHashUrl 单 hash
- 修复管理端办件抽屉「查看大图」域名尾点（origin + BASE_URL("./") 拼接）
- 新增 flowError 口径层与办理页内联失败条，审批失败提示可读、不泄漏堆栈
- 审批节点抽屉新增「预览候选人」真入口 + AssigneePreviewModal（只读，不写回定义）
- 线级停发/恢复失败改为单条错误面，避免同错双 toast
- 审批抽屉核心区/高级设置分层；插入菜单常用/高级分组
- 新增 FlowAssignEmbed 选人 iframe 父侧宿主（origin/source/信封/context 四校验）
- 修复 /diagram、/assign-preview 面包屑误显示「流程编辑器」

package.json

@@ -15,8 +15,9 @@
         "api:gen": "alova gen -f",
         "typecheck": "vue-tsc --noEmit",
         "test:line-offline": "esbuild tests/line-offline.test.ts --bundle --platform=node --format=esm --target=node20 --external:node:* --outfile=node_modules/.cache/line-offline.test.mjs && node node_modules/.cache/line-offline.test.mjs",
+        "test:unit": "esbuild tests/line-offline.test.ts tests/app-url.test.ts tests/flow-error.test.ts tests/assign-preview.test.ts tests/convert-roundtrip.test.ts --bundle --platform=node --format=esm --target=node20 --external:node:* --outbase=tests --outdir=node_modules/.cache/unit && node --test node_modules/.cache/unit",
         "test:component": "vitest run",
-        "test": "npm run test:line-offline && npm run test:component"
+        "test": "npm run test:unit && npm run test:component"
     },
     "dependencies": {
         "@open-file-viewer/core": "^0.1.43",