ENG-2380 Extract shared section header and align Foundations section width on landing page

[jsmorabito]

Reviewer brief

• Result: Foundations uses the shared SectionHeader (eyebrow "Foundations", title "A shared structure for research work in motion") and lines up with the other landing page sections.
• Review focus: SectionHeader now renders the eyebrow conditionally with mb-3 in place of the title's mt-3, so existing headings keep the same spacing. The Foundations container goes from max-w-6xl to max-w-7xl, which scales its cards up slightly at wide desktop widths.
• Follow-up: ENG-2316 (stacked on this PR) builds the new About section on this header.

Verification

• pnpm ci:validate passes.
• Checked in the browser that Foundations, Plugins and Resources share the same left edge and width at desktop width, and that existing section headings are unchanged.

Loom video

Foundation Section Alignment and Heading Updates

Scope check

• Ran $scope-check against ENG-2380 and the final diff.
• Scope beyond Done When: None.

Standards check

• Ran $dg-pr-adherence-check against the final diff and PR metadata.

Local delegated full review

• Ran a comprehensive review of the entire final diff in a subagent with a fresh context. Use $dg-delegated-full-review when no other full-review workflow is available.

🤖 Generated with Claude Code

[supabase]

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[linear-code]

ENG-2380

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Project	Deployment	Actions	Updated
discourse-graph	Ready	Preview	Oct 9, 2026 9:26pm UTC

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.