feat(pagestream): open pages in page host, card animation, webview fade-in
- Remove inline iframe browsing — click/Enter opens URL in real page host window
- Card-to-page ghost animation: card expands to page host size, page opens at
that exact position, ghost stays as backdrop until window renders
- Close animation: page host closes, ghost shrinks back to card
- Remove bottom navbar and browse container (page host has its own floating nav)
- Fix peek-card border CSS bug: both :host([bordered]) and :host(:not([bordered]))
matched, giving every card a border regardless
- Inject shadow DOM style overrides for opaque card backgrounds (no transparency
on transparent windows) with hardcoded hex colors
- Active card uses max-width: 518px instead of transform: scale() to avoid
overflow clipping of rounded corners
- Pagestream window: full screen width, 80% screen height
- Page host webview fade-in: detect page background color on dom-ready, set as
backing color on webview element, fade from opacity 0→1 to prevent white flash