Motivation & Problem

In #633, active table/view/database selection was synchronized to the connections sidebar tree (_ConnectionsTreeSelectionScope) with fluid animated selection styling (_PgTreeRow) across PostgreSQL, MySQL, SQLite, Redis, and MongoDB.

However, extension drivers (e.g. ClickHouse) render their schema hierarchy using SduiTreeBuilder in connections_panel_extension.dart. Currently, SduiTreeBuilder does not receive or support an active selection identifier (selectedNodeId or selectedObject), which means selecting a table or view in an extension connection does not highlight the active node in the sidebar tree.

Proposed Scope

1. In SduiTreeBuilder:
   • Add selectedNodeId (or active selection predicate) parameter.
   • Forward selection from _ConnectionsTreeSelectionScope via _ExtensionConnectionTile.
   • Add animated selection container styling (subtle primary background tint, primary border outline, semibold typography) matching _PgTreeRow selection state.
2. In connections_panel_extension.dart:
   • Forward active extension selection from _ConnectionsTreeSelectionScope to SduiTreeBuilder.
3. Add widget tests verifying that selecting an extension node highlights the corresponding row in the SDUI tree.

Acceptance Criteria

• Selecting a table or view in an extension connection visually highlights the active row in the sidebar tree.
• The highlight styling matches the native tree row design tokens (120ms animation, primary background tint, subtle border).
• Deselecting or switching objects updates or clears the highlight smoothly.
• Widget tests pass for SduiTreeBuilder active node highlighting.