#19041 test(gallery): cover classic new tab page

What changed

Add a gallery entry for the legacy (variant-A) NewTabPage still selectable from the host while the newer NewTabScreen is dogfooded.

The entry covers:

• Terminal, Browser, and Agent switching, including Tab and Shift+Tab
• ! and ? prefix edits, Escape clearing, and omnibar keyboard activation
• project/folder chooser filtering and keyboard selection
• default-kind cycling
• existing-session, All sessions, and submit host receipts

It removes only the NewTabPage#KindIcon and NewTabPage#NewTabPage allowlist rows. The NewTabScreen gallery and all composer/changes lanes remain untouched.

Validation

• bun run typecheck
• bun test test/gallery-coverage.test.ts (6 pass; 55 entries / 533 variants)
• bun run gallery:build
• bunx vp fmt src/agent-session/acpmux/NewTabPage.gallery.tsx --check
• git diff --check
• Happy DOM smoke: kind switch, ! prefix, default-kind receipt, open-session receipt, and project chooser selection

Gallery build emitted the existing ::highlight(...) CSS parser warnings; the build passed.

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Summary by cubic

Adds a gallery entry covering the classic (variant-A) NewTabPage so its keyboard flows and host receipts stay visible while the newer NewTabScreen is dogfooded.

The entry exercises Terminal/Browser/Agent switching, ! and ? prefix edits, Escape clearing, omnibar keyboard activation, project chooser filtering, default-kind cycling, and existing-session, All sessions, and submit host receipts. It removes the KindIcon and NewTabPage rows from the coverage allowlist; the NewTabScreen gallery and all composer/changes lanes are untouched.

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[!NOTE]
Low Risk
Test and gallery-only changes; no production UI or runtime behavior.

Overview
Adds a component gallery entry for the legacy classic NewTabPage (agent-pane.new-tab-page) so it stays covered while NewTabScreen is dogfooded.

The entry wires fixtures, a receipt wrapper on host callbacks (onSubmit, onJump, onOpenSession, etc.), and Play scenarios for kind switching, !/? prefixes, Tab/omnibar keyboard navigation, Escape clear, project chooser, default-kind cycling, open-session, and “All sessions”. It declares covers for NewTabPage and KindIcon plus layout/perf gallery checks.

gallery-coverage.allowlist.json drops the two NewTabPage.tsx rows that are now satisfied by this entry.

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