Rebrand main area widget as Data Dictionary

[dauglyon]

## Summary

• Rebranded the main-area experience from "Tenant Explorer" to "Data Dictionary".
• Updated command/context-menu labels from "Open in tab" to "Open Data Dictionary".
• Updated tab icon behavior:
  • Tenant tabs use users icon
  • User data tabs use user-circle icon
• Updated table UI structure in the Data Dictionary panel:
  • Added section header rows with count pills for Databases, Tables, and Table Column Schema
  • Tables and Table Column Schema now render dedicated column-header rows
  • Removed the old prose schema subheader
• Implemented restore behavior for main-area Data Dictionary tabs across browser refresh:
  • Added WidgetTracker + ILayoutRestorer wiring for tenant tabs
  • Added stateDB-backed fallback restore for open tabs and per-tab selection state
  • Restored tab order to match current main-area tab order

Test plan

• Open tenant and user-data nodes from tree; labels show Open Data Dictionary.
• Verify tab headers/icons:
  • tenant tab -> users icon
  • user data tab -> user-circle icon
• Verify Data Dictionary layout:
  • Databases has one section header row
  • Tables has section header + column header row
  • Table Column Schema has section header + column header row
  • header rows use header coloring
• Open multiple Data Dictionary tabs, refresh browser, and verify tabs restore.
• Verify restored tabs keep order after refresh.
• Build passes: uv run jlpm build.

Notes

• No server/API contract changes.
• Restore logic includes both Jupyter layout restorer integration and a stateDB fallback for reliability.

[github-actions]

Prerelease: pr-15

Wheel will be attached once the build completes. Updated on each push.