Audit public API and SemVer surface (#103)

api/README.md

@@ -61,6 +61,21 @@ rejects stale, missing, duplicate, or erased entries; and verifies
 `API-COVERAGE.md`. Regenerate that report with
 `python3 tools/check_api_coverage.py --write`.
 
+The reviewed first-release public surface is stored in
+[`SEMVER-BASELINE.json`](SEMVER-BASELINE.json), with the decisions and migration
+recipes rendered in [`SEMVER-AUDIT.md`](SEMVER-AUDIT.md). The audit compares
+mapping/export coverage, normalized Rust declarations, feature sets, ownership,
+async and error contracts, thread-safety boundaries, and public dependency
+types. Record a deliberate baseline only after reviewing its SemVer impact,
+then verify it and write reproducible evidence:
+
+```sh
+cargo run --locked -p metacrate-ci-matrix -- api-baseline-write
+cargo run --locked -p metacrate-ci-matrix -- api-audit \
+  --evidence /tmp/metacrate-api-audit.json
+cmp /tmp/metacrate-api-audit.json ci/evidence/api-audit.json
+```
+
 Native implementations replace whole generated types where practical. The
 generated module retains the catalog markers and re-exports the hand-written
 type; member-level implementations use an explicit generator registry. This