feat(landing): add /skill-watch page wired to frames.ag dataset

[Markeljan]

Summary

Adds a new Skill Watch page at /skill-watch that pulls audited agent skills from the microchipgnu/skill-watch dataset on frames.ag and renders them as a live, sortable, filterable inventory. The "Examples" link in the header and both footer columns now point at the new page; the existing /examples route stays in place for now.

What's on the page

1. Hero with live count + most-recent scan timestamp
2. Snapshot stats (6 cards: skills monitored, with findings, clean, avg overall score, avg security score, total installs)
3. Findings-by-severity bars + grade distribution chart (headlined by the modal grade — e.g. "Mostly C · 261")
4. OWASP top categories — click any row to filter the inventory below by that AST-NN
5. Inventory grid with paginated cards (24 per page), search, filter by grade / vuln status / OWASP, and 7-way sort
6. CTA linking to install + the upstream dataset

Inventory UX

• Pagination — 24 cards per page with "Show 24 more" + "Show all N" actions; resets to 24 whenever a filter changes
• Sticky filter bar at top-[64px] with backdrop-blur so filters stay reachable while scrolling
• Mobile sort — sort row is visible at all viewports with horizontal-scroll fallback (was previously hidden md:flex)
• OWASP bars → table filter — bars dispatch a skill-watch:filter-owasp event that the table listens for, then smooth-scrolls to #inventory. The bar count (e.g. AST05 = 260) matches the filter result exactly
• Reset filters affordance + empty-state with reset button
• Search matches name, owner, repo, description, OWASP id, and rule id
• Accessibility — aria-pressed on every toggle, role="img" + aria-label on grade chips and capability badges, aria-live="polite" on the result counter, scroll-mt-24 on #inventory to clear the fixed header

Performance note for reviewers

The upstream JSON is ~4.5 MB. Passing the raw response (including the per-field evidence block with URLs + excerpts on every record) to the client component embeds the full payload in the page HTML and stalls React hydration — clicks become unresponsive. Fixed by slimEntity() in page.tsx which drops evidence before serialization, shrinking the inline payload from ~3.8 MB to ~600 KB. Next.js's fetch data cache also refuses the 4.5 MB response (>2 MB limit) — that's a non-fatal warning at build time; ISR still works, each revalidate hits the API fresh.

Test plan

• bun run build — /skill-watch route emits at ~6.5 kB, static, 1h revalidate
• bun run lint clean
• Desktop preview: filter by grade/vuln/OWASP, sort by each option, pagination, OWASP bar click → applies filter + scrolls to inventory
• Mobile (375px) preview: search input full-width, filters wrap, sort row scrolls horizontally
• AST05 click → 260/295 cards (matches bar count exactly)
• Reset filters → counter back to 295/295, visible count back to 24
• Header and footer links resolve to /skill-watch

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