[jdjioe5-cpu]

Summary

Closes #29. Fulfills Roadmap row \M1-39\ (Phase 1, M0 Validate, Priority P1).

This PR publishes the authoritative contract surface reference documentation:

• **\docs/ERRORS.md**: Complete reference for all 32 active #[contracterror]\ codes across registry and vault, specifying exact trigger conditions, caller guidance (retryable vs terminal), and explicit documentation for retired codes 1 (\Paused) and 27 (\TokenTransferFailed).
• **\docs/EVENTS.md**: Complete catalog of all 7 emitted contract events across payee lifecycle and vault operations, including \schema_version = 1, precise field types, stroops integer scaling (\10^7\ stroops per unit), and the rationale for immutable payee payout snapshotting (Hard rule 2).
• Updated \README.md\ and \docs/ARCHITECTURE_ESSENTIALS.md\ to link to these contract surface references.
• Updated \ROADMAP.md\ to mark \M1-39\ as \DONE\ with an entry in the Changelog.

Contract Surface Verification & Count Comparison

1. Error Codes Match (\�rrors.rs\ vs \docs/ERRORS.md)

• Active error variants in \contracts/kinlock/src/errors.rs: 32
• Documented error sections in \docs/ERRORS.md: 32
• Retired codes noted: 2 (code 1 \Paused, code 27 \TokenTransferFailed)
• Exact count comparison:
  • Code count: \32\ active variants in \�rrors.rs\
  • Doc count: \32\ sections in \docs/ERRORS.md\
  • Delta: \