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** — dropping columns, changing types, or adding non-null columns without defaults (crashes on deploy). 2. **API Contract breaking changes** — modifying existing REST/GraphQL properties, removing endpoints, or adding required query fields that break old clients. 3. **Serialization mismatches** — editing properties in serialized payloads (JSON, Protobuf, XML) without deserialization fallbacks. 4. **Library Contract Drift** — changing a public method signature in a shared library without a deprecated wrapper. 5. **Environment Configuration drift** — introducing new required config keys (`.env` / OS vars) without defaults or fallback. Expand/contract migration rules, per-format serialization fallbacks, and the breaking-vs-additive API checklist: read `references/checks.md` before scanning. **Scope:** honor `.coalmine.json` `schemaPaths` / `migrationDirs` if set — scan those globs/dirs; else infer by inspecting the repo. ## Discipline - **Style Drift Resolution (Fix mode):** when an approved fix touches mixed-style code, conform the minority patterns to the dominant style (highest average usage) to minimize churn — never start a standalone style refactor. ## Fix mode (choice-gated) In Agent Context, after the report, present via `ask_question`: