#19750 cmux-next: New Tab suggestions are an omnibar popover

Typing in the New Tab field ("Ask anything or type a URL") had three problems:

• The suggestions showed inline and pushed the page down.
• "reddit" showed nothing.
• Blank browser tabs were offered as "about:blank workspace-N".

Leo asked for a real omnibar. Bead: cx-gl7dv, taken over from op-next-motion.

What changed

• The rows float in a popover anchored under the composer. It is a solid theme surface on the dropdown layer, and the page under it no longer moves.
• The rows are now an omnibar, and the top row is highlighted and is what Return does:
  • A word that completes an address comes first. "reddit" gives reddit.com, from visited pages and then a built-in list of top sites. Return opens it in a browser tab.
  • Matching open tabs and workspaces follow. Picking one switches to it.
  • "Search the web for …" and "Ask <agent>" come last. The Ask row shows the chip's model as its detail.
  • For other text, "Ask <agent>" is the top row, followed by the web search and the matches. If there is no agent to ask, Return still shows the existing "no agent" note instead of searching.
  • An address keeps its "open" row on top.
• Tabs and pages still on an about: page are left out of the popover's rows. A split page's Open Tabs list still lists them, so a blank tab can be moved.
• An address completes from 3 letters, so "go" or "no" stays a prompt.

This widens cx-e2aa's rule (rows only for addresses and other tabs, 2026-10-09). Workspaces, Search and Ask now also get rows, as Leo asked on 2026-10-12.

Verification

• New behavior test webviews/test/new-tab-omnibar.test.tsx, run with bun test webviews/test/new-tab-omnibar.test.tsx:
  • Red on 546a6b44: 0 pass, 3 fail. reddit.com was missing, there was no .nt-popover, and a prompt had no Ask row.
  • Green on the head: 3 pass.
• The existing New Tab tests (new-tab-no-agent, new-tab-send-button, new-tab-default-agent) and ui-rules pass. bun run check passes, including the layers, type-scale, format and lint checks.
• New gallery scenario typed-reddit shows "reddit" typed over the page. typed-tab-match and typed-address notes are updated.
• Localization: one new key, newTab.row.searchFor ("Search the web for {text}"), with all 21 locales. Non-English values are marked needs_review. generated/strings.json was regenerated (gen-strings.mjs --check agentPane passes). The Ask and Switch-to-workspace rows reuse existing keys.
• Web-only change: no Swift or Rust is touched.

Changelog

• Changed: The New Tab field's suggestions float in a popover under it, and it completes addresses like "reddit", matches tabs and workspaces, and offers web search and Ask.

Showcase

Open the live gallery

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