Agentic UI: Lower the session composer footer controls to hug the panel's bottom edge

[shaunandrews]

Proposed Changes

The actions below the chat composer (including the sidebar toggle) are unevently spaced, with more space below than above. To help visual balance, this PR moves them down a bit.

Testing Instructions

1. Run the app and open any site's chat session.
2. Look at the controls below the composer (chat history icon + New chat).
3. They should sit closer to the bottom edge of the chat panel than before, with a slightly larger gap between them and the composer card.
4. Tab to both controls and confirm the focus ring renders fully — the strip's own bottom padding keeps it clear of the panel's overflow: hidden edge.
5. Check in both light and dark color schemes, and at both narrow and wide panel widths (the preview panel open and closed).

How AI was used in this PR

Claude Code compared the composer footer's positioning between trunk and the explore-site-centric-conversation-chrome design-preview branch, identified the single declaration responsible for the difference, and ported it. The change was reviewed by hand.

[wpmobilebot]

📊 Performance Test Results

Comparing ef50ca1 vs trunk

app-size

Metric	trunk	ef50ca1	Diff	Change
App Size (Mac)	1375.40 MB	1375.40 MB	+0.00 MB	⚪ 0.0%

site-editor

Metric	trunk	ef50ca1	Diff	Change
load	1090 ms	1048 ms	42 ms	⚪ 0.0%

site-startup

Metric	trunk	ef50ca1	Diff	Change
siteCreation	6481 ms	6499 ms	+18 ms	⚪ 0.0%
siteStartup	2373 ms	2375 ms	+2 ms	⚪ 0.0%

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Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)

[bcotrim]

LGTM 👍