Add screenshots for all major UI features to README

[geier]

Context

The README has been updated with a comprehensive feature showcase, but currently only has one screenshot (docs/active-session.png showing an active chat session). The README would be much more compelling with screenshots of all major features.

Goal

Capture and add screenshots for each major UI feature to the docs/ directory, and reference them in the appropriate README sections.

Screenshots Needed

1. Project Picker (docs/project-picker.png) -- the home/welcome page showing recent projects, Open Project and Clone Repository buttons
2. Directory Browser (docs/directory-browser.png) -- the project dialog with fuzzy search and directory listing
3. Git Clone (docs/git-clone.png) -- the clone dialog with the embedded terminal showing progress
4. MCP Dialog (docs/mcp-dialog.png) -- the MCP server list with status indicators and toggles
5. MCP Add Server (docs/mcp-add-server.png) -- the form for adding a new MCP server
6. Command Palette (docs/command-palette.png) -- the palette open with some entries visible
7. Hint Mode (docs/hint-mode.png) -- the overlay with letter labels on clickable elements
8. Settings Page (docs/settings.png) -- the settings page showing one of the tabs (Providers or Appearance)
9. Sound Settings (docs/sound-settings.png) -- the Sounds tab in settings
10. Saved Prompts (docs/saved-prompts.png) -- the Prompts tab with some saved prompts
11. Multi-Project Sidebar (docs/multi-project-sidebar.png) -- sidebar showing multiple open projects with status badges
12. Auto-Accept Indicator (docs/auto-accept.png) -- session header showing the auto-approve toggle

Files to Modify

• docs/ -- add new screenshot PNG files
• README.md -- add ![Description](docs/filename.png) references under the relevant feature sections

Acceptance Criteria

• Each screenshot is a clean capture (no personal data, API keys, or sensitive info visible)
• Screenshots use a reasonable resolution (ideally consistent, e.g., 1200px wide)
• Light or dark theme is consistent across all screenshots
• README references each screenshot under its corresponding feature section
• Images are optimized for web (reasonable file size, PNG format)