ADR-017: contract versioning — core crate's semver is the contract version (OQ-10 resolved)

docs/architecture/decisions/001-crate-split.md

@@ -81,7 +81,13 @@ crate. A consumer binary links at most one driver.
 - A version-coordination duty: the core's trait surface is a contract
   the engine crates must track. Version bumps in core must be adopted
   by engines in lockstep when the contract changes (minor/major
-  discipline; no trait-default drift).
+  discipline; no trait-default drift). *(Discharged 2026-10-06: the
+  duty's concrete shape is the versioning discipline —
+  [ADR-017](017-contract-versioning.md), OQ-10's resolution: the
+  core crate's semver is the contract version, change classes +
+  lockstep duties pinned, the pairing tracked by manifest pin +
+  version-stamped contract suite + docs; released engines on a
+  breaking change keep their pinned majors — nothing forced.)*
 - Slightly more crate plumbing; naming/publishing overhead.
 - Consumers who want *both* engines in one binary (rare, unsupported-by
   design) cannot get a both-features build today.
@@ -96,6 +102,8 @@ crate. A consumer binary links at most one driver.
   link-collision constraint motivates this split.
 - [ADR-004](004-postgres-driver.md) — the Postgres driver choice.
 - OQ-10 (`docs/architecture/open-questions.md`) — trait-versioning
-  duties created here.
+  duties created here; resolved by
+  [ADR-017](017-contract-versioning.md); OQ-11 — the fork-follow-through
+  residue (per [ADR-013](013-fold-substrate-into-sqlite.md) §4).
 [ADR-003]: 003-sqlite-driver.md
 [ADR-004]: 004-postgres-driver.md