Replace separate project and activity navigation with a fixed-height two-line button and a shared workspace menu. Browse local, remote and channel projects, preview sessions on hover, restore the last opened conversation, and show ten recent conversations alongside active work.
Preserve project settings, recovery actions, draft leave guards and completion reminders. Reuse conversation summaries and windowed lists without hover fetches or polling.
Validation: focused component and App tests, real Electron layout and interaction checks, typecheck and lint passed. The earlier full suite timed out and reported Supervisor settings/layout failures.
Release note: 左上角统一项目与活动入口，支持分类查找、悬停预览和最近 10 个会话；双行按钮整体点击，保留项目设置与跨项目会话切换。
