Add type-safe artifact lane resolution

docs/policy/architecture.md

@@ -73,6 +73,12 @@ Extract modules own artifact semantics, prompt use, response schemas, and
 domain interpretation. Domain-specific concepts remain in the relevant module,
 validator, shared domain helper, and artifact contract.
 
+Typed artifact registrations declare one stable artifact kind and exact Go
+type from extraction through merge, normalization, and semantic validation.
+Pipeline resolution requires a compatible codec and matching kind-specific
+variants before a typed lane can be accepted. Framework-owned erasure remains
+private and must report type incompatibility as an error rather than a panic.
+
 Auxiliary references provide context or disambiguation. They are not source
 evidence and must not be converted into source references.
 
@@ -104,6 +110,11 @@ extract, merge, and normalize stages. Validators receive immutable stage output
 and make an explicit whole-output decision: approve, approve with warnings, or
 reject.
 
+Typed artifact validators receive the domain value directly. Chunk validators
+receive source-zone chunks, while serialized validators receive immutable
+representation bytes and declared schema metadata. A validator registered for
+one target or artifact kind cannot satisfy an incompatible selection.
+
 Rejection is a recorded pipeline outcome, not a framework execution error.
 Validator execution failures are framework errors. Rejected output does not
 advance to the next stage.