Task 287: Landing Page Summary Cards + E2E Bug Fix

Status: DONE

Motivation

1. E2E bug: reports.spec.ts line 379 used ep.slug which doesn't exist on the manifest episode type (only ep.path exists). This caused the "no NaN in video timestamp links" test to navigate to /episodes/undefined.html — silently passing because an error page also has 0 NaN links.
2. Landing page UX: Summary analysis pages were listed as a plain <ul> with just titles, while episode pages got styled cards with summaries and metadata. This was an inconsistency in visual presentation.

Changes

1. E2E fix: Changed ep.slug to ep.path in the NaN-in-links regression test
2. Landing page: Summary pages now render as a responsive grid of cards (.summary-card) with page descriptions, matching the episode card style
3. Type update: Added summary field to SiteManifest.summaryPages type
4. Build update: buildManifest() now includes summary text from SummaryReport.summary
5. CSS: Added .summary-cards grid layout (auto-fill, min 280px columns)
6. Test fixes: Updated test data to include required summary field

Verification

• TypeScript typecheck passes (0 errors)
• All 2,147 TS unit tests pass
• Build produces correct output with summary cards and descriptions