fix: handle null activeElement in _spaceCatcher AND fix: guard _moveManual and _ariaChecked against dom-repeat race AND MORE

[javier-godoy]

Close #49
Close #50

Summary by CodeRabbit

• Bug Fixes

  • Dot navigation now follows the actually rendered dots to prevent off-by-one and out-of-bounds navigation.
  • Click handling consolidated to a single delegated listener and cleaned up on detach to avoid duplicate handlers or leaks.
  • Dot-related styles are only initialized when dots exist.

• Accessibility

  • Dot controls expose accurate aria-checked states and per-dot aria-labels.
  • Keyboard/focus detection for advancing slides improved.