perf(main): optimize sidebar spring animation and eliminate full-slot offscreen Opacity compositing #900

Summary

In MainScreenState._buildAnimatedSidebar (lib/features/main_screen/main_screen.dart), sidebar collapse and expand are animated using physics springs (_sidebarWidthSpring).

Inside the animation builder (lines 1361–1364):

child: Opacity(
  opacity: contentOpacity,
  child: material.RepaintBoundary(
    child: _ConnectionsPanelSlot(...),
  ),
),

Because Opacity is placed outside RepaintBoundary and animates continuously on every tick of the spring (60–120 Hz), Flutter cannot reuse the cached raster layer of _ConnectionsPanelSlot. Instead, Flutter is forced to allocate and composite an intermediate offscreen buffer (saveLayer) on every frame for the entire connection tree (all database connections, schemas, tables, views, status indicators, badges).

On Linux and Windows systems (especially with integrated graphics or software compositing), this causes significant frame drops and stutter during sidebar collapse/expand.

Scope

• Ensure the static content of _ConnectionsPanelSlot is cached in its raster layer without invalidating it via parent opacity, or use layer-based opacity / avoid full offscreen compositing when opacity is 1.0 or 0.0.
• When sidebar width reaches collapse threshold, cleanly detach or offstage the connection panel to stop ticker and paint passes.

Out of scope

• Changing the physics parameters of QueryaSpring.snappy.