- DashboardRail: always expanded at 140px width (was collapsible 280px)
- Overview tab: removed UsageChart, Account (1/3) + Quota (2/3) side by side
- Usage tab: removed QuotaDisplay, UsageChart spans full width
- Global transparency increased (light surface 0.30, card 0.38; dark surface 0.20, card 0.28)
- DiagnosticsPanel fully internationalized (32 zh + 32 en keys)
- Added Vitest test infrastructure with 12 passing tests
- Added DashboardShell, dashboard-tabs, DashboardRail components

- 新增 ChatTestPanel 组件（对话测试标签页）
- 新增 stream.ts 流式聊天工具函数及测试
- 新增 filter.go 模型过滤功能及测试
- 左侧模型列表支持搜索和滚动
- 右侧对话区域支持流式输出、文件上传
- 优化毛玻璃效果和布局一致性
- 更新 i18n 中英文案
- 重构 server.go 相关 API 端点

- Reset messages to single user message per send (overwrite, not append)
- Only send current prompt in API request (no conversation history)
- Guard onDone against empty assistant bubble (trim check)
- Add auto-scroll to bottom via chatBodyRef + scrollToBottom()

- Add finalized flag to readStream preventing duplicate onDone calls
- Guard all three completion paths (reader end, [DONE], usage)
- Add 4 new test cases covering usage+DONE, DONE+reader, double DONE