fix(izui): promote content to child-content when opened from parent window
Extensions explicitly passing role:'content' bypassed the inference that
detects parentWindowId and assigns child-content. This meant ESC did
nothing for pages opened from groups (escPolicy returns 'nothing' for
content role in active session).
Fix: after role assignment, promote content → child-content when
parentWindowId is set. Background/extension-host windows have null
parentWindowId so they're unaffected.