tui: cannot remove stale projects from /open list; desktop crashes on non-existent project

Description

Two related issues around handling non-existent project directories:

TUI — /open and /project commands show stale projects that can't be removed:

When a project directory is moved or deleted, the /open and /project commands still list it as a previously opened project. There is no way to remove stale entries. If the user selects one, the session fails or hangs.

Desktop — Settings > Projects shows non-existent projects, and opening them crashes the app:

In the desktop app, the Settings > Projects panel lists previously opened projects. If a project directory has been moved or deleted, it still appears in the list. When the user tries to open it, the app throws:

ClientError: UnexpectedStatus
    at i (oc://renderer/assets/health-BdaR9NAA.js:1:41042)

原因：
{
  status: 500
}

The desktop app becomes unresponsive and must be manually restarted.

Steps to reproduce

TUI:

1. Open a project in TUI (/open or startup)
2. Move or delete that project directory from disk
3. Run /open or /project again — the old project still appears in the list
4. There is no option to remove it from the list

Desktop:

1. Open a project in the desktop app
2. Move or delete that project directory from disk
3. Go to Settings > Projects — the old project still appears
4. Try to open it — the app crashes with ClientError: UnexpectedStatus (status: 500) and must be restarted

Expected Behavior

• TUI: /open and /project should detect stale (non-existent) project entries and either remove them automatically or provide a way to delete them from the list
• Desktop: Settings > Projects should detect stale entries and either remove them or show a clear error message ("Project directory not found") instead of crashing the app

Actual Behavior

• TUI: Stale projects persist in /open and /project lists with no way to clean them up
• Desktop: Settings > Projects shows stale entries; opening one crashes the app with a 500 error requiring a full restart

Additional Context

• opencode version: 2.0.3
• OS: Windows_NT 10.0.26200 (win32 x64)
• Terminal: xterm-256color (TUI mode)
• Shell: cmd.exe
• Install/channel: npm global, latest
• Active plugins: None
• This is a common scenario when reorganizing project directories or migrating between machines