Add Google Workspace connector

## Summary
Add Google Drive/Workspace integration for document sync and possibly Gmail/calendar-style agent actions.

## User Value
Tracking this as a GitHub issue moves the backlog item out of a private markdown file and gives the team a clear place to prioritize, design, implement, and validate the work.

## Proposed Behavior
Separate Drive file sync from Gmail/Calendar actions. Define OAuth/admin consent model, Google native file export handling, user/workspace scoping, and whether the default chat experience gets a Google tab.

## Acceptance Criteria
- [ ] The requested behavior is designed or implemented for the relevant SimpleChat surfaces.
- [ ] Permission, configuration, and existing-feature interactions are accounted for.
- [ ] Tests, documentation, or validation notes are added as appropriate.

## Notes
- Source backlog entry: Google Workspace Connector
- Source file: priv-simplechat-2/grouped_feature_fix_backlog.md
- Backlog status: New / Research
- Current anchors: `google_workspace` is named as a future File Sync source type but not implemented.
- Proposed roadmap priority: P2
- Proposed roadmap size: XL