Trade Barriers tracker UI: /trade-barriers + per-agreement pages

[xrendan]

Summary

Companion to BuildCanada/york_factory#33. Renders the interprovincial trade barriers tracker against the new york_factory CMS endpoints. Replaces the old Supabase-backed BuildCanada/TradeBarriers standalone app — frontend lives here, CMS lives in york_factory.

• Index page at `/trade-barriers`: status overview cards + progress bar, activity chart (chart.js), KPI cards (stale agreements / recent negotiations YoY), filterable list of agreements, FAQ modal.
• Detail page at `/trade-barriers/`: agreement summary, description, jurisdiction status table with per-jurisdiction history, status timeline. Replaces the original `AgreementModal` with a real page so each agreement has a stable URL, sitemap entry, and SEO metadata.
• SEO: `generateMetadata` on detail pages produces per-agreement title, description, OG tags, and canonical URL. Shared OG image at `/public/trade-barriers/og.png`. Sitemap includes `/trade-barriers` plus one entry per agreement slug (gracefully skipped if API unavailable at build).
• Data layer in `src/lib/api/trade-barriers.ts` wraps:
  • `GET /api/v1/trade_barriers/agreements`
  • `GET /api/v1/trade_barriers/agreements/`
  • `GET /api/v1/trade_barriers/themes`
  • `GET /api/v1/warehouse/jurisdictions`
• Build: pages are `dynamic = "force-dynamic"` so the build does not depend on york_factory#33 being deployed first. They SSR at request time once the API is live.
• Reused deps: chart.js / react-chartjs-2 / lucide-react / @base-ui/react Dialog — all already in TradingPost. No new dependencies. Did not port the shadcn-heavy UI from the source repo; replaced with simple Tailwind-based equivalents.
• Intentionally dropped: `SimpleAnalytics`, `AgreementForm`, `AddAgreement`, `EditAgreement`, `ProtectedRoute`, `ThemeManagement`, `AgreementModal` (admin lives in york_factory; modal replaced by detail page).

To surface on /projects

`/projects` is data-driven by york_factory's tools API. After york_factory#33 deploys, add a Tool entry via admin with `externalUrl=/trade-barriers` to surface the tracker on the projects grid. No code change needed here.

Test plan

• `pnpm build` clean (tested locally — both `/trade-barriers` and `/trade-barriers/[slug]` build as ƒ Dynamic).
• TypeScript clean.
• Lint clean on new files (the 1 unrelated lint error in `tracker/commitments/page.tsx` is pre-existing).
• After york_factory#33 deploys: visit `/trade-barriers` — verify KPIs, filters, list, chart render. Click a card → detail page renders with SEO metadata.
• `/sitemap.xml` includes `/trade-barriers` and per-slug entries.

Sequencing

york_factory#33 should merge + deploy before this lands so the API endpoints exist when this hits prod. (Build is decoupled, but runtime requests will 404 until then.)

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