drift-canarylisted

# Drift Canary (Contract & Schema Drift Audit) <!-- SHARED:LANGUAGE_HEADER --> Audit code to ensure changes do not break backward compatibility or cause database/API mismatches. ## Auditing Categories 1. **Breaking Schema Migrations** — Database schema edits that drop columns, change types, or add non-null columns without defaults (causes crashes during deployments). 2. **API Contract breaking changes** — Modifying existing REST/GraphQL properties, removing API endpoints, or adding required query fields that break old clients. 3. **Serialization mismatches** — Editing properties in serialized data payloads (JSON, Protobuf, XML) without maintaining deserialization fallbacks. 4. **Library Contract Drift** — Changing the signature of public methods in a shared library without maintaining deprecated wrappers. 5. **Environment Configuration drift** — Introducing new required configuration keys (`.env` or OS variables) without providing defaults or fallback logic. Expand/contract migration rules, per-format serialization fallbacks, and the breaking-vs-additive API checklist: read `references/checks.md` before scanning. ## Discipline - **Style Drift Resolution (applies in Fix mode):** when an approved compatibility fix touches an area where multiple code styles are mixed, conform the minority patterns to the most dominant/frequent style (highest average usage) in the project to minimize churn — never start a standalone style refactor. (เรื่อง Style Drift ถ้ามีการปนเปกันมาก ๆ ให