[TheGreatAxios]

Summary

• Rewrote README.md, ARCHITECTURE.md, IMPLEMENTATION.md, PRODUCT.md against the current tree (Workbench as an Interchange client, mail-threaded chat, Myra as the one shipped agent), each under its line budget.
• Stripped VENDORED.md's ledger to one sentence per row, removed ticket ids and the kill-date-test column.
• Removed ticket references from DESIGN.md; content otherwise unchanged.
• Deleted every docs/ file describing a retired feature or past decision (workbench tenancy, folded mail, onboarding connect cards, seed reconciliation, proposals, images, etc.).
• Rewrote the four surviving docs/ files (GLOSSARY.md, local-dev.md, sidecar-provisioners.md, package-migrations.md) against the code, each under 60 lines.
• Updated AGENTS.md's Docs map to list the surviving docs/ files.

Test plan

• CI

[linear-code]

CL-8317