feat(browser): tabs (multiple embedded documents)

#406 in DioxusLabs/blitz — merged 2026-04-28

Summary

Implements the following features from the Browser UI backlog (#363):

• Tabs
• Status bar
• Menu item to clear HTTP cache

It also refactors the Browser UI into multiple files.

Out-of-scope items deliberately deferred for follow-ups:

• drag-to-reorder tabs
• target=_blank → new tab
• keyboard shortcuts (Ctrl+T/W/Tab),
• pre-warmed hidden viewport (layout hidden tabs with correct viewport)
• pinning / right-click menu / thumbnails, session persistence.

Implementation details:

• One <web-view> per tab, rendered with display: none on inactive tabs so style resolution and asset fetching continue in the background while paint is skipped.
• Per-tab Tab struct: history, DocumentLoader, document, node_handle, html_source, title. Each tab loads independently; closing a tab drops its loader and cancels in-flight fetches.
• Tab strip with click-to-switch, "+" new-tab, "×" close (hidden when only one tab remains). Rounded upper corners, seamless join with the urlbar.
• Live tab titles via find_title_node() cached into a per-tab Signal at load time (falls back to URL).
• Window title reactively follows the active tab's title via the chrome's <title> element.
• Back/forward buttons render disabled (dim, click is a no-op) when there's no history in that direction.
• All chrome handlers (back/forward/refresh/home/menu/URL bar) operate on the active tab read at call time.