agent-sessions-layout

When working on the Agents workbench layout, always follow these guidelines:

1. Read the Specification First

The authoritative specification for the Agents layout lives at:

src/vs/sessions/LAYOUT.md

Before making any changes to the layout code, read and understand the current spec. It defines:

• The fixed layout structure (grid tree, part positions, default sizes)
• Which parts are included/excluded and their visibility defaults
• Titlebar configuration and custom menu IDs
• Editor modal overlay behavior and sizing
• Part visibility API and events
• Agent session part classes and storage keys
• Workbench contributions and lifecycle
• CSS classes and file structure