Sitemap UX uplift — instant search, lane jump-nav, per-lane counts

Changes

The /sitemap/ page lifts to a frontier-level directory experience. Lands on top of the L1/L2 sync wave that ships 184 canonical anchors across 8 primary lanes + a support layer.

Instant search

• Search input above the lane grid with placeholder “Search 184 pages — try ‘tau’, ‘dark matter’, ‘verify’…”.
• Live-filters all 184 mini-cards by case-insensitive substring match against link title.
• Hides whole lane cards when all their links are filtered out.
• Status chip below the input shows “ of 184 pages match ''" or "Showing all 184 pages." when empty.
• Deep-linkable: filter state syncs to URL via ?q=<query> so reviewers can share filtered views.
• Empty state (“No pages match your search.”) with three suggestion buttons (results, verify, challenge) that apply the suggestion on click.
• Clear button (×) inside the input resets state.
• Keyboard: / focuses the input from anywhere on the page; Esc while focused clears the query, then blurs.
• Debounced (80 ms) — no jank while typing.

Lane jump-nav with scroll-spy

• Sticky pill-row above the lane grid: 8 lane pills + a Support pill.
• Each pill is an in-page anchor (#lane-discover, #lane-program, …, #lane-support).
• Active state syncs to scroll position via IntersectionObserver — the pill for the lane currently in the viewport gets highlighted with the brand colour.
• Mobile: jump-nav becomes horizontally scrollable.

Per-lane counts and totals

• Each lane card header now carries an “ entries" chip (e.g. "20 entries" for Impact, "34 entries" for Results).
• Intro section gains a totals chip strip: “8 primary lanes · 184 canonical pages”.

Validation hardening

scripts/assert_v4_sitemap.py extended with assertions for:

• id="sitemap-search-input" and role="search" present.
• class="sitemap-jump" with ≥9 pills covering all 8 lanes + support.
• data-sitemap-lane-count attribute on each lane card.
• data-sitemap-link-title attribute on each mini-card (drives client-side search).
• /assets/js/sitemap-search.js script tag loaded.
• id="sitemap-empty" empty-state container present.
• class="sitemap-totals" chip in intro.

Progressive enhancement

The page is fully usable without JavaScript:

• All 184 mini-cards render server-side.
• Without JS, the search input is inert (filter doesn’t apply) but the input doesn’t break the page.
• Jump-nav pills are plain anchor links — they still scroll to lane sections without JS.
• Reduced-motion users get all CSS transitions disabled.

Files touched

• sitemap.md — Liquid additions for search, jump-nav, totals, count chips, empty state.
• _sass/_sitemap.scss — styles for all UX components, including a prefers-reduced-motion override.
• assets/js/sitemap-search.js (new, 200 lines vanilla JS) — search filter, URL sync, jump-nav scroll-spy, keyboard shortcuts.
• _layouts/program-doc.html — conditional script load gated by page.support_type == "sitemap" so no global JS bundle change.
• scripts/assert_v4_sitemap.py — UX-component assertions.