Space settings: configurable root path with file browser #58

Summary

Add the ability to change the root path of a space within a repository, and use a file browser to select it during space setup.

Details

Currently, when creating a git-backed space, the sub-path is typed in manually as a text field. This should be improved:

1. Space root path in settings: In the space detail view (Settings > Spaces > [space]), add a "Root path" setting that shows the current subPath and allows changing it. For read-only (git-backed) spaces, this setting should be read-only and display the configured path.

2. File browser in wizard: In the "Add from Git" wizard step, the sub-path field should support both:

   • Direct text input (current behavior)
   • A "Browse" button that clones the repo first (from root), then opens a file browser to select the desired directory

3. Wizard flow for browsing: When using the browse option:

   • Clone the full repo from root
   • Show a file browser (directory picker, not file picker)
   • User selects the desired directory
   • Set the sub-path from the selected directory
   • Update the space settings accordingly

4. Space settings in repo: Space configuration should be saved in the repository (e.g., .cept/space-config.json) so that users across devices get a consistent experience. Read-only spaces cannot have their settings changed.

Related

• Part of the space management improvements from PR Fix space management: /g/ URLs, auto-setup, sync, and wizard #52
• Depends on the file browser component already available in SettingsModal.tsx (FileBrowser)

Acceptance Criteria

• Space detail view shows the root path
• Wizard supports browsing for sub-path
• Space config is persisted in the repo for cross-device consistency
• Read-only spaces show settings as read-only