feat: change default workspace layout with terminal, problems panel, and agent sidebar

[Cheezeiii365]

Description

Update the default workspace layout to populate with actual content panes instead of just the root view.

Proposed Layout

The new default layout should include:

• Bottom terminal: Split horizontally in half
  • Left half: Small terminal pane
  • Right half: Problems panel
• Left Side*: Large terminal pane
• Right side: Browser pane
• Right sidebar: Agent chat history

Current State

Currently, the workspace only displays the root view by default without pre-populated panes.

Expected Behavior

When opening a workspace, users should see a functional multi-pane layout ready for:

• Terminal-based workflows (terminal on left)
• Issue/problem tracking (problems panel on right)
• Web content viewing (browser pane)
• Agent interaction history (sidebar)

This provides a more complete IDE experience out of the box.