Reorganize brain: projects/ top level, rename filenames, update homepage

- Moved everything from ideas/passepartout/ to projects/passepartout/
- Moved legal structures to projects/flags/
- Created missing _index.org files for all subdirectories
- Stripped redundant passepartout- prefix from filenames
- Rewrote root _index.org as generalized brain index (projects + concepts)
- Updated Hugo nav to Projects/Concepts
- Updated build script section descriptions
- Deleted stale ideas/passepartout-economics.md orphan

projects/passepartout/strategy/compliance/un-cefact.org

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+:PROPERTIES:
+:ID:       6a5884c8-e9b5-477e-bbf6-aa9ffd967739
+:ID:       auto-un-cefact
+:CREATED:  [2026-05-23 Sat]
+:END:
+#+title: UN/CEFACT (United Nations Centre for Trade Facilitation and Electronic Business)
+#+filetags: :passepartout:compliance:framework:un:
+
+EU, UK, Japan, Australia, Canada (2024), Brazil, India, South Korea, and most
+of Asia and Africa. The US (GAAP) is the major holdout.
+
+Why it matters: [[id:fc736aec-ef53-4759-9787-62bc8deea2e7][IFRS]] 17 and IFRS 9 are algorithmically complex rule sets.
+Getting an actuarial model or credit loss calculation wrong is a financial
+reporting error. The gate stack's ACL2 prover can verify that the calculation
+implementations match the standard's mathematical requirements. First-mover
+advantage: IFRS 17 was the largest accounting change in a decade. Implementation
+was a crisis for insurers. The next wave (IFRS 18, sustainability disclosures
+via ISSB) is coming. A verified IFRS gate package is a unique value proposition.
+
+** UN/CEFACT (UN Centre for Trade Facilitation and Electronic Business)
+
+UN standards for electronic data interchange (EDI), trade facilitation, and
+cross-border data exchange. Key standards: UN/EDIFACT (trade data), Core
+Component Library (CCL), Multi-Modal Transport Reference Data Model. Basis
+for WTO Trade Facilitation Agreement compliance.
+
+Who must comply: Customs authorities, logistics providers, trade finance banks,
+exporters/importers in 170+ WTO member countries.
+
+Why it matters: Cross-border trade data exchange is rule-intensive (tariff
+classification, rules of origin, customs valuation, sanitary/phytosanitary
+requirements). The gate stack can encode trade compliance rules and prove that
+every cross-border data exchange satisfies the applicable regulation. First-mover
+advantage: trade compliance is a $15B market dominated by legacy SAP/Oracle
+modules and customs brokerages. None use verification.
+