* feat(screenshot): add Ctrl+C shortcut to copy selection without saving
Add Ctrl+C shortcut in interactive region selection mode to immediately
copy the current selection (or hovered snap target) to clipboard without
saving to a file.
- Works during mid-drag, on hovered targets, or on existing selections
- Bypasses file saving and forces clipboard output
- Emits aborted status in JSON mode so external callers (such as Quick
Capture) exit cleanly without launching an annotation editor
- Exits cleanly without error if triggered with no selection
- Updates HUD items with Ctrl+C copy shortcut
- Hides corner resize handles and maintains crosshair cursor while dragging with Ctrl held
* fix(screenshot): bypass stdout and scroll phase when copyOnly is active
- Disable stdout output when copyOnly is active to ensure the image
is copied to the clipboard instead of being written to stdout.
- Write 'Copied to clipboard' to stderr if --stdout was originally passed.
- Bypass entering scrollPhase in finishSelection() if copyOnly is set,
immediately capturing and copying the selected region.