Restructure Data section: Sources dropdown + standalone FactBase

[OAGr]

Problem

The current "Data" dropdown in the top nav is confusing:

1. "Sources" is overloaded — one page with 3 unrelated tabs (Resources, Publications, Data Sources)
2. "Data Sources" dropdown item goes to the same page as "Sources" (just pre-selects tab 3)
3. Three of four dropdown items contain the word "source" — Sources, Data Sources, Source Checks — but mean very different things
4. FactBase is buried — it redirects to a wiki article (/wiki/E1019), making it feel like documentation instead of an interactive data explorer. Its 5 sub-pages (Facts Explorer, Properties, Coverage, Records) are hidden behind wiki article stubs
5. No organizing principle — the dropdown is a flat list of 4 unrelated things. "Data" as a label is too generic (Organizations, People, etc. are also "data")

Proposal

Split "Data" into two nav items: Sources (dropdown) and FactBase (standalone link with sidebar).

Conceptual split

Sources = citation and verification infrastructure. "Where does information come from, and can we trust it?"

• Resources (21k external documents we cite)
• Publications (99 venues that publish those documents)
• Source Checks (automated verification of facts against sources)
• Data Sources (pipelines that ingest structured data)

FactBase = structured, temporal, queryable knowledge. "What structured facts does the wiki know about entities?"

• Not about sourcing — it's the structured knowledge LAYER that sits on top of sources
• Complex enough to need its own sidebar (5 explorer pages + 4 detail page types)

New nav structure

Before: Search | Entities ▾ | Research ▾ | Policy ▾ | Data ▾      | About | Internal
After:  Search | Entities ▾ | Research ▾ | Policy ▾ | Sources ▾   | FactBase | About | Internal

Sources dropdown (4 items):

Sources ▾
  Resources       → /resources
  Publications    → /publications
  Source Checks   → /source-checks
  Data Sources    → /data-sources

FactBase: standalone link → /factbase (sidebar handles sub-navigation)

URL changes

Almost zero URL churn. Existing URLs mostly stay the same — pages just stop redirecting and render directly.

FactBase pages — same URLs, stop redirecting through wiki articles:

URL	Before	After
/factbase	redirect → /wiki/E1019	Renders overview directly
/factbase/facts	redirect → /wiki/E1020	Renders facts explorer directly
/factbase/properties	redirect → /wiki/E1021	Renders properties directly
/factbase/entity-coverage	redirect → /wiki/E1022	Renders coverage directly
/factbase/records	redirect → /wiki/E1026	Renders records directly
/factbase/entity/[id]	Entity detail	Same
/factbase/fact/[id]	Fact detail	Same
/factbase/property/[id]	Property detail	Same
/factbase/record/[id]	Record detail	Same

All FactBase pages get a persistent sidebar via a new layout.tsx.

Sources pages — decompose the tabbed page:

URL	Before	After
/sources	Big tabbed page	Removed (nav now links directly to sections)
/resources	Redirect → /sources	Standalone resources page (table + enrichment pipeline + domain breakdown)
/resources/[id]	Resource detail	Same
/publications	Standalone page	Same
/publications/[id]	Publication detail	Same
/source-checks	Standalone page	Same
/source-checks/[type]/[id]	Verdict detail	Same
/data-sources	Redirect → /sources?tab=data-sources	Standalone data sources page

No redirects from old URLs needed — no external users on these pages.

FactBase sidebar

FACTBASE                    (defaultOpen: true)
  Overview                  → /factbase
  Facts Explorer            → /factbase/facts
  Properties                → /factbase/properties
  Entity Coverage           → /factbase/entity-coverage
  Records                   → /factbase/records

TOP ENTITIES                (defaultOpen: false, dynamic top 30 by fact count)
  Anthropic (45)            → /factbase/entity/anthropic
  OpenAI (38)               → /factbase/entity/openai
  ...

Uses existing WikiSidebar + SidebarProvider infrastructure (same pattern as /internal/layout.tsx).

Implementation

New files (3):

• apps/web/src/app/factbase/layout.tsx — sidebar layout for all FactBase pages
• apps/web/src/app/resources/page.tsx — standalone resources page (content extracted from old sources/page.tsx)
• apps/web/src/app/data-sources/page.tsx — standalone data sources page (wraps existing DataSourcesContent)

Key modifications:

• nav-links.ts — Sources dropdown (4 items) + FactBase standalone link
• wiki-nav.ts — update getFactBaseNav() links from /wiki/E* to /factbase/*
• 5 FactBase redirect pages → render components directly instead of redirecting
• factbase/entity/[entityId]/page.tsx — remove inline sidebar wrapping (layout handles it)
• Breadcrumb updates in FactBase detail pages
• Delete sources-tabs.tsx (no more tabs)
• Update links in home page, search, FactsSection.tsx, factbase-overview-content.tsx

Unchanged:

• All API routes (/api/source-checks/*, /api/data-sources/*, /api/resources/*)
• All CLI commands
• /source-checks pages — completely unchanged
• /publications pages — completely unchanged
• FactBase detail pages — same URLs, just breadcrumb updates
• MDX files in content/docs/factbase/ — keep as-is (harmless, preserve wiki IDs)

[OAGr]

Branch: claude/deploy-tasks-verify-cmd

Closing — the data section restructure shipped via PR #3675. Forward work (Sources hub, FactBase polish, cross-linking, entity page refactor) lives in #3699. — Discussion review 2026-04-08.