Developer docs changelog

Notable updates to /dev/docs and related developer guidance (not product release notes).

• 2026-04-08

  • Economics aligned to whitepaper v2 via src/constants/economics.ts.
  • Marketplace agent connectivity test: POST /api/marketplace/developer/agents/[agentId]/test (owner-only sandbox probe).
  • A2A framework profiles + conformance checklist on A2A protocol.
  • Sidebar: active route highlighting + filter search.