docs: replace README with project SSOT, move dev setup to docs/

Michael Angelo Riverarequested to merge
arivera/readme-ssot-update into main

Summary

The repo README was just a local dev setup guide with "Coming soon" at the top. This replaces it with the project Source of Truth document that came out of the Feb 2026 GKG offsite. One of the action items from that offsite was consolidating project knowledge into a single reference since information was scattered across epics, design docs, Slack threads, and people's heads.

The new README covers:

  • Project architecture and data flow
  • Epic tracker with all workstream links
  • Complete repository map (Orbit, Siphon, infra, docs)
  • Helm chart inventory (production, dev, observability)
  • Infrastructure details (sandbox, staging, Terraform)
  • Usage billing references
  • Team contacts

The previous dev setup content moves to docs/dev/LOCAL_DEVELOPMENT.md, alongside the existing infrastructure and runbook docs where it belongs.

What changed

  • README.md -- replaced with SSOT document
  • docs/dev/LOCAL_DEVELOPMENT.md -- new file, former README content with updated heading

Test plan

  • Verify all links in the new README resolve correctly
  • Confirm docs/dev/LOCAL_DEVELOPMENT.md setup instructions are still accurate

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