[codex] Improve SPM calculator launch flow

[MaxGhenis]

What changed

This PR makes the calculator behave like a launchable poverty-analysis product instead of an internal saved-reports shell.

• adds a dedicated country landing page for the calculator with SPM-focused framing and clear household/report entry points
• routes / to /:countryId instead of dropping new users directly into saved reports
• deep-links household users past the standalone scope picker with ?scope=household
• upgrades the empty saved-analyses screen so first-time users get actionable next steps
• fixes the shared standard layout so main content uses the full viewport width on mobile instead of rendering in a narrow strip
• tightens calculator metadata around poverty and household analysis

Why

The previous first-run experience was weak for launch:

• root users landed in an empty "saved reports" screen
• the app framed itself as a generic calculator instead of an SPM-oriented analysis tool
• the fastest household path still went through an avoidable scope step
• mobile layout had a real width bug in the shared shell

User impact

• first-time visitors now see a real launch page with clear CTAs
• household users can get into the custom-household flow faster
• empty-state pages no longer dead-end
• mobile users can actually use the launch and saved-analysis screens without the content collapsing

Validation

• cd app && bun run vitest --run src/tests/unit/components/IngredientReadView.test.tsx src/tests/unit/pages/Reports.page.test.tsx src/tests/unit/pathways/population/launchPrefill.test.ts
• bun run --filter=@policyengine/calculator typecheck
• cd app && bun run typecheck
• bun run --filter=@policyengine/calculator build
• manual browser verification in local Next dev server for /, /us, /us/households/create?scope=household, and /us/reports on desktop and narrow mobile viewport

[vercel]

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Project	Deployment	Actions	Updated (UTC)
policyengine-app-v2	Ready	Preview, Comment	Apr 13, 2026 10:24am
policyengine-calculator	Ready	Preview, Comment	Apr 13, 2026 10:24am
policyengine-website	Ready	Preview, Comment	Apr 13, 2026 10:24am

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
policyengine-calculator-next	Skipped		Apr 13, 2026 10:24am

[policyengine]

Solid launch flow improvements. The new dedicated landing page, improved routing, and mobile layout fix all work well together. A few minor observations:

What works well:

• The CalculatorLaunchPage component properly uses design tokens throughout (colors, spacing, typography)
• Text correctly uses sentence case everywhere
• The mobile layout fix in StandardLayout (tw:max-w-full on mobile, sm:tw:max-w-[calc(100vw-300px)] on desktop) properly addresses the width bug
• The ?scope=household deep-link pattern with getPopulationLaunchPrefill is clean and well-tested
• Empty state improvements in Reports.page give first-time users clear next steps
• Routing changes (/ → /:countryId → launch page instead of /reports) make sense for a product launch
• IngredientReadView's custom emptyState prop is a good pattern
• Tests cover the new behavior

Minor observations:

1. In CalculatorLaunchPage.tsx:101, the country fallback (LAUNCH_CONTENT[countryId] ?? LAUNCH_CONTENT.us) is defensive but countries outside us/uk will see US content. This seems acceptable for now since only those two are defined.

2. The removed "Title Section" in IngredientReadView.tsx (lines 84-97 in the diff) means the title now only appears in the header area. The test confirms this renders exactly once, which is correct.

3. StandardLayout.tsx:59 - the responsive max-width pattern looks correct: mobile gets full width, desktop gets sidebar-aware width. The ordering matters here (mobile-first, then sm: override).

The PR achieves its stated goals: better first-run experience, SPM-focused framing, faster household path, and mobile layout fix. No bugs, edge cases, or security issues found.