SharePoint connector

[fuseraft]

Implement the SharePoint connector described in docs/features/connectors.md under "Planned Connectors" — part of the Short Term (v0.2–0.3) roadmap.

Planned scope (from docs):

• Site and library traversal
• Document metadata extraction (author, modified date, version)
• Managed metadata and taxonomy integration
• Incremental updates (delta sync)
• Permissions mapping (visibility metadata)

Target CLI surface:

compendium connect sharepoint \
  --site https://company.sharepoint.com/sites/architecture \
  --bundle my-catalog \
  --type Document \
  --auth interactive

Depends on the connector plugin architecture issue (IConnector + ConnectorRegistry).