feat(app): reorganize settings into grouped pages with shared row components

[iamnbutler]

What

Settings cleanup:

• Page division. The nav is split into two groups: app settings (General, Providers, Team, Beta) and This Mac (Ace Helper, Computer use, Updates). The old This Mac page mixed the helper, the CLI, Tailscale, the directory, the team secret, tools and troubleshooting. Team connectivity now has its own Team page. Ace Helper keeps the helper status, its log, the CLI and tools. Each tool row shows its path and version, which replaces the Troubleshooting disclosure.
• Standard components in settings-layout.tsx:
  • Page and Group: a section title, plus an optional action on the right.
  • Row: a label, at most one description line, and the control on the right.
  • TextRow: a text setting. Save appears only when the value has changed, and Escape discards the edit.
  • Segmented (used for theme), Select, Value (read-only status), and Confirm (an inline destructive confirmation; it replaces four copies of the same markup).
• Less text. Page descriptions, the "How it works" and "What happens during an update" disclosures, and the long row explanations are gone. Every row has at most one short line.

Verification

• bun types and bun run ci pass.
• Checked General, Ace Helper, Team and Computer use in an isolated bun desktop dev build.

Built in Ace

Written with Claude Code outside Ace while dogfooding. I checked the layout with desktop tools against a dev build. Nothing Ace lacks blocked this work.