Add sideways chart previews to the existing unlisted impact page

[lksbrssr]

Updates the existing cryptic preview, without launching field velocity

Targets main after #154 and the existing /impact-preview-eb61fba1b98e/ route. This is the PR to merge for the slide effect on that page. Draft #155 is separate and remains the future public-detail switch-on.

Latest refinement: whiter inactive cards

Per Lukas's follow-up, unselected cards displaced to the side now fade toward white in light mode, rather than receiving a darker gray mask. Dark mode retains its exact original mask. The veil does not intercept clicks; no chart, geometry, data or route logic changed in this refinement.

Local candidate gallery crop, showing the CSS included in 14def61. The old gray-mask screenshots in the history are superseded.

Slide behavior

• Real chart previews slide sideways from beneath a multi-view cover, displacing and visually de-emphasizing neighbors behind a divider.
• Applies across all four field tabs; each preview opens only its own chart. Single-view and evidence-only cards still open directly.
• Mobile uses gallery-local scrolling and a next-card peek. One spread is active at a time.
• Preserves chart/data flips, exact shareable URLs, keyboard/focus/history behavior, data, API and methodology.
• Public detail mounts remain absent. Preview remains unlisted/noindex, with no /impact/ promotion or discovery links added.

Verified

• Head 14def61661145dd6dee8bbd090bd2b617e1e9f67: 85 tests, TypeScript, production build, diff check and independent incremental review PASS. The first local build hit process-spawn EAGAIN; the isolated retry passed without source changes.
• Added white-mask regression failed before the CSS change and passes afterward.
• Final production browser checks at 1440/390/320px verify the rendered light mask is 60% white, dark masking matches the pre-change baseline, pointer events pass through, and page geometry is unchanged.
• The earlier slide pass ran 88 browser cases across all four fields. Its narrow focus-restoration fix passed 3 scrolled-dismissal and 15 clipboard/fresh-link/keyboard/history cases. Those records predate only this color-only refinement.
• Existing unrelated document-width deltas remain unchanged (8px at 1440/390; 15px at 320 with native scrollbars). No physical touch-device or native screen-reader test is claimed.
• Latest hosted Vercel deployment is green. The parent repeated all six light/dark color-and-geometry checks on the hosted branch at 1440/390/320px. All three embedded image URLs were verified byte-for-byte. PR remains unmerged; these checks do not claim a production merge.

Before: overlay fan

Interactive deployment preview · Detailed scope and screenshot provenance

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Project	Deployment	Actions	Updated
plrd.org	Ready	Preview	Sep 10, 2026 9:36am UTC