feat: introduce redesigned settings center and harden cross-platform updates

[mssssss123]

Summary

• Replace the legacy settings UI with a redesigned, structured settings center.
• Add two-level navigation for agent and extension settings.
• Provide dedicated configuration pages for:
  • General preferences and editor behavior
  • Model providers and agent models
  • Routing, memory, always-on agents, web search, and scheduled tasks
  • External integrations
  • MCP servers and Office preview
  • Security, privacy, advanced settings, and update information
• Improve visual hierarchy, spacing, typography, selected states, and keyboard focus styles.
• Collapse dependent configuration fields when Web Search, Cron, or Router features are disabled while preserving saved values.
• Preserve masked secrets and support explicit editing without unintentionally clearing existing credentials.
• Keep legacy settings deep links working with the new navigation structure.
• Improve update and restart compatibility across platforms:
  • Resolve Bash dynamically on Windows.
  • Support PILOTDECK_BASH_PATH.
  • Use a native Windows restart command when appropriate.
  • Return clearer errors when the update runtime cannot be found.

Testing

• pnpm --dir ui build
• pnpm --dir ui exec vitest run server/services/updateRuntime.test.js src/components/settingsNew/navigation.spec.ts src/components/settingsNew/view/agentSearch/utils/webSearchConfig.spec.ts
  • 3 test files passed
  • 13 tests passed
• Targeted ESLint checks for the updated settings components
• Manually verified the General, Web Search, Scheduled Tasks, MCP Servers, and Office Preview settings pages