Reduced extra terminal noise while creating TUI workspaces

Improvements

• CoreAdded a configurable default shell for terminals and agent shell commands, with a Desktop setting to manage it.
• TerminalHid provider connection checks until onboarding is complete.
• TerminalRestored the default toast timeout when no custom duration is provided.@OpeOginni
• CoreFixed issue with opencode upgrade failing for bun installs unless in a directory with package.json