Add Shadow DOM support

[mehmetnadir]

Description

Elements inside Shadow DOM (<shadow-root>) are not accessible via document.querySelector.

Expected behavior

cdpilot click "my-component >>> .inner-button"
# or
cdpilot click --shadow "my-component" ".inner-button"

Implementation hints

• Use DOM.describeNode + DOM.resolveNode for shadow roots
• Or use element.shadowRoot.querySelector() in JS evaluation
• Pierce syntax (>>>) is a common convention

Good first issue — interesting CDP exploration.