Share import declaration preparation

docs/roadmap/implementation.md

@@ -111,6 +111,8 @@ Test selected and unused fallbacks. Defer the no-base path to Stages 3–4.
 
 ## Stage 3 — Share import declaration preparation
 
+**Status:** Complete. Focused import and placement checks passed.
+
 In `import_acquisition.go`, extract the context-independent first pass of
 `walkDeclarations` so both normal traversal and the contextless path can
 use it. Prepare from the already parsed declaration specs, apply

internal/engine/import_acquisition.go

@@ -242,19 +242,27 @@ func (s *importTraversal) checkInitialLimits() *Diagnostic {
 	return nil
 }
 
-func (s *importTraversal) walkDeclarations(basePath string, declarations []importDeclarationSpec, depth int, parentDestination Path, sourceIndex int) []Diagnostic {
+func prepareImportDeclarations(declarations []importDeclarationSpec, defaults ImportDefaults, parentDestination Path) ([]resolvedImportPolicy, []Diagnostic) {
 	policies := make([]resolvedImportPolicy, len(declarations))
 	for index, spec := range declarations {
-		policy, diagnostics := resolveImportPolicy(spec, s.policy.importDefaults)
+		policy, diagnostics := resolveImportPolicy(spec, defaults)
 		if len(diagnostics) != 0 {
-			return diagnostics
+			return nil, diagnostics
 		}
 		if policy.placement == PlacementModeSequenceItem && len(appendDestination(parentDestination, policy.destination).segments) == 0 {
 			site := spec.fieldSites["placement"]
-			return []Diagnostic{{Code: CodeImportInvalid, Severity: SeverityError, Path: site.path.clone(), Message: "sequence-item placement requires a nonempty destination", Primary: cloneLocation(&site.location)}}
+			return nil, []Diagnostic{{Code: CodeImportInvalid, Severity: SeverityError, Path: site.path.clone(), Message: "sequence-item placement requires a nonempty destination", Primary: cloneLocation(&site.location)}}
 		}
 		policies[index] = policy
 	}
+	return policies, nil
+}
+
+func (s *importTraversal) walkDeclarations(basePath string, declarations []importDeclarationSpec, depth int, parentDestination Path, sourceIndex int) []Diagnostic {
+	policies, diagnostics := prepareImportDeclarations(declarations, s.policy.importDefaults, parentDestination)
+	if len(diagnostics) != 0 {
+		return diagnostics
+	}
 	for index, spec := range declarations {
 		policy := policies[index]
 		var selection importSelection