Improve summary detail layout

[MyButtermilk]

Summary

• align the transcript title with the full summary layout instead of offsetting it to the content column
• move the YouTube source action into the sticky header, with compact responsive and mobile-menu variants
• keep the summary table of contents at its final sticky position from the initial render

Why

The summary-specific header padding left an unnecessary empty column and reduced the available title width. The standalone YouTube source link also sat above the summary grid, so the table of contents shifted upward before reaching its sticky offset.

User impact

Summary pages use the available horizontal space more effectively, source actions stay grouped together, and the table of contents no longer moves when scrolling begins.

Validation

• npm run check
• npm run test — 84 library tests and 35 component tests passed
• npm run test:i18n
• Prettier and git diff --check
• visual browser checks at 2048 px and the 1440 px breakpoint
• verified the table of contents had the same measured Y position before and after 420 px of scrolling

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep the YouTube label visible for smoke widths

At the default desktop smoke viewport, this label is display: none because it is hidden until the 2xl breakpoint, leaving only decorative SVGs visible. scripts/smoke_frontend_browser.py still waits for document.body.innerText to contain “Open on YouTube” on /transcript/youtube-processing-smoke, and the smoke browser starts at 1280px wide, so that route will time out even though the link exists. Keep visible text at md/lg widths or update the smoke to assert the aria label instead.

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