#430 fix(desktop): open terminal presets as pane instead of new tab

Summary

• Change default behavior when selecting a terminal preset to add as a split pane in the current tab instead of creating a new tab
• Falls back to creating a new tab if no active tab exists
• Context menu still offers both "Open as New Tab" and "Open as Pane in Current Tab" options

Test plan

• Click preset in sidebar with existing tab → should add pane (split)
• Click preset in sidebar with no tabs → should create new tab
• Use Cmd+K command dialog to select preset → should add pane
• Right-click context menu → should still offer both options

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Preset activation now opens content as a pane within the active tab instead of creating a new tab, improving workflow efficiency. Previous behavior is preserved when no active workspace or tab exists.

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