feat(testing): spec-conformance test for AdcpError code names against error-code.json enum

[bokelley]

Context

The AGENT_SUSPENDED, AGENT_BLOCKED, REQUEST_AUTH_UNRECOGNIZED_AGENT, and INVALID_BILLING_MODEL codes shipped for months as non-spec (caught in #375 / fixed in PR #393). Drift was only caught by manual review.

Add an automated test that walks all AdcpError(\"CODE\", ...) raise sites in src/adcp/ (AST or grep) and asserts the code is in the canonical static/schemas/source/enums/error-code.json enum (or has the X_ vendor prefix). Catches future drift at PR time.

Acceptance Criteria

• New tests/test_error_code_conformance.py
• Walks all AdcpError(\"CODE\", ...) raise sites in src/adcp/
• Asserts code is in static/schemas/source/enums/error-code.json enum or has X_ vendor prefix
• Runs in CI; fails CI on any non-spec code

Refs

• Issue Tier 2 commercial-identity error codes don't conform to AdCP spec — cross-tenant oracle risk #375, PR fix(decisioning): Tier 2 codes → spec-conformant PERMISSION_DENIED (#375) #393

[bokelley]

Triage

Classification: Feature request
Bucket(s): client, handlers
Status: drafting-pr
Milestone: (omitted — no target version specified)

What the experts said:

• code-reviewer: approved — no blockers; stale comments and schema fixture hardening addressed in review→fix cycle
• ad-tech-protocol-expert: approved — X_ prefix aligns with spec's extension model; AUTH_INVALID allowlist is protocol-correct given the spec's explicit forward declaration of the AUTH_REQUIRED split
• dx-expert: AUTH_INVALID is a named future spec code — do not use X_AUTH_INVALID; allowlist approach preserves the semantic distinction the spec plans to formalize

My take: Issue is clear-cut and all criteria for Execute are met. One design question (rename AUTH_INVALID → AUTH_REQUIRED vs. allowlist it as a provisional spec code) is surfaced in the PR body for reviewer decision; both approaches are valid and the PR uses the lower-scope one.

PR: #436 — AST conformance test + rename INTERNAL_ERROR → X_INTERNAL_ERROR, BILLING_NOT_PERMITTED_FOR_AGENT → X_BILLING_NOT_PERMITTED_FOR_AGENT. 231 tests pass.

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Triaged by Claude Code. Session: https://claude.ai/code/session_01SpT9n4csqsXxbogX4q6GHo

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