chore(openspec): archive engineering-docs and phase-2-production-ready changes

- engineering-docs → archive/2026-03-29-engineering-docs (63/63 tasks complete)
- phase-2-production-ready → archive/2026-03-29-phase-2-production-ready (89/89 tasks complete)
- openspec/specs/ synced with all Phase 1 + Phase 2 + engineering-docs capabilities (22 specs total)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

openspec/specs/code-walkthroughs/spec.md

@@ -0,0 +1,27 @@
+## ADDED Requirements
+
+### Requirement: Annotated code walkthrough documents
+The system SHALL include a document (`docs/engineering/06-walkthroughs.md`) containing three annotated end-to-end walkthroughs of the system's critical flows, with file:line references to actual source code.
+
+#### Scenario: Token issuance walkthrough complete
+- **WHEN** a new engineer reads the token issuance walkthrough
+- **THEN** they SHALL be guided step by step from: HTTP POST /oauth2/token → Express router → auth middleware → OAuth2Controller → OAuth2Service → CredentialRepository → Vault/bcrypt credential check → Redis token cache check → JWT signing (src/utils/jwt.ts) → AuditService.logEvent → HTTP 200 response
+- **AND** every step SHALL reference the actual file and line number where it occurs
+
+#### Scenario: Agent registration walkthrough complete
+- **WHEN** a new engineer reads the agent registration walkthrough
+- **THEN** they SHALL be guided step by step from: HTTP POST /agents → auth middleware → validation middleware → AgentController → AgentService.createAgent → input validation (src/utils/validators.ts) → AgentRepository.create → PostgreSQL INSERT → AuditService.logEvent → HTTP 201 response with agent object
+- **AND** every step SHALL reference the actual file and line number
+
+#### Scenario: Credential rotation walkthrough complete
+- **WHEN** a new engineer reads the credential rotation walkthrough
+- **THEN** they SHALL be guided step by step from: HTTP POST /agents/:id/credentials/:credId/rotate → auth middleware → CredentialController → CredentialService.rotateCredential → old credential revocation → new secret generation (src/utils/crypto.ts) → Vault write or bcrypt hash → CredentialRepository.update → token revocation for old credentials → AuditService.logEvent → HTTP 200 response
+- **AND** every step SHALL reference the actual file and line number
+
+#### Scenario: Walkthroughs include version reference
+- **WHEN** a new engineer reads any walkthrough
+- **THEN** the document SHALL include a header stating the commit hash it was last verified against, so engineers know if the walkthrough may have drifted from the current code
+
+#### Scenario: Each walkthrough annotates why, not just what
+- **WHEN** a new engineer reads a walkthrough step
+- **THEN** each step SHALL explain not just what the code does but WHY — e.g., why Redis is checked before signing a new JWT, why constant-time comparison is used for credential verification, why audit logging happens after persistence not before