Fix mobile guided chat dock layering and reduce over-reserved bottom spacing

[Copilot]

This PR resolves the mobile guided chat layout regression where the persistent composer and bottom nav competed for space and excessive bottom padding pushed key UI (including navigation affordances) out of view. It aligns dock positioning with the persistent subnav and normalizes mobile bottom reserves to pb-40.

• Composer dock + subnav layering

  • Keeps SurfaceMobileSubnav visible on compact viewports while guided mobile chat is active.
  • Positions the guided mobile persistent composer dock above the subnav via fixed bottom offset that includes safe-area inset.

• Bottom spacing normalization (pb-40)

  • Replaces oversized mobile transcript/panel reserve usage with pb-40 in guided chat surfaces:
    • transcript container (renderChatMessages)
    • guided right-panel scroll area
    • guided mobile card container
    • guided mobile chat content wrapper

• Snapshot/string tests updated for layout contract

  • Updates source-level assertions to match:
    • new dock offset class
    • pb-40 usage in guided mobile layout
    • compact viewport subnav render condition

guidedMobileComposerDock
  ? "fixed inset-x-0 bottom-[calc(4.5rem+env(safe-area-inset-bottom,0px))] z-[80] ..."
  : "...";

{isCompactViewport && <SurfaceMobileSubnav current="chat" />}

// guided mobile content reserves
"pb-40"

Original prompt

Create a clean PR that fixes the mobile chat layout issues:

• Wrap the mobile persistent composer dock (ChatInput) in a fixed-position container at the bottom of the screen, positioned just above the SurfaceMobileSubnav.
• Reduce the excessive bottom padding from pb-[22rem] to pb-40 in the relevant places in vessel/src/app/page.tsx (renderChatMessages area, guided panels, etc.) so that the VisualNavigationHub and other elements are no longer pushed out of view on mobile.

Do not include any build artifacts (.next/trace files). Keep the change minimal, focused, and reviewable. Base it on the latest main branch.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
shipyard	Ready	Preview, Comment	Jun 28, 2026 4:21pm

[sonarqubecloud]

Quality Gate failed

Failed conditions
E Maintainability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

Catch issues before they fail your Quality Gate with our IDE extension SonarQube for IDE