fix(shortcuts): allow ESC to close dialogs when terminal is focused

[IShaalan]

Summary

• When a dialog (Help, Settings, New Task) is open and a terminal has focus, pressing ESC now correctly closes the dialog instead of being swallowed by xterm.js
• matchesGlobalShortcut now also passes dialogSafe shortcuts through xterm when a .dialog-overlay is present in the DOM
• ESC still reaches the terminal normally when no dialog is open (vim, readline, etc. unaffected)

Test plan

• Open keyboard shortcuts dialog (Cmd+/ or F1), click into a terminal, press ESC — dialog should close
• Open settings dialog, click into a terminal, press ESC — dialog should close
• With no dialog open, press ESC in terminal — should reach the terminal as before (e.g. exit vim insert mode)
• Cmd+/ and F1 still toggle the help dialog from terminal focus (unchanged, already had global: true)

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