feat: graph validation and custom JSON-LD

- seo_schema (seoschema, E8) with the C17 server rules: invalid JSON with
  line and column, non-objects, 16 KB, depth 8, a literal <script and a
  type outside the kind's list refused; the value re-serialised
- a custom node with a generated @id merges into it (schema.merged save
  notice), other nodes are appended to the graph
- seo_primary_parent (seoparent) for article types; both values stored
  in the entry data on every locale row
- the seo_graph widget action (E9 data), P1 primary_gone and the P2
  schema type and breadcrumb trail rows
- GET /_seo/api/v1/graph and MCP seo_get_graph; seo_set_url_seo and
  apply_batch accept primary_parent and schema

The graph tool lands with the validation: the operations parity test
binds the seo_graph widget action to its tool.

classes/owner.go

@@ -5,6 +5,7 @@ import (
 	"net/url"
 	"strings"
 
+	"git.golem15.com/golem15/sm-seo-plugin/classes/schema"
 	"git.golem15.com/golem15/sm-seo-plugin/models"
 	"git.golem15.com/golem15/summercms/modules/pact"
 	"gorm.io/gorm"
@@ -126,6 +127,9 @@ func (s *Service) SetURLSEO(ctx context.Context, tx *gorm.DB, in URLSEOWrite) (U
 	for _, column := range EntryColumns {
 		known[column] = true
 	}
+	for _, column := range DataColumns {
+		known[column] = true
+	}
 	for column, raw := range in.Values {
 		v := strings.TrimSpace(raw)
 		switch {
@@ -148,6 +152,27 @@ func (s *Service) SetURLSEO(ctx context.Context, tx *gorm.DB, in URLSEOWrite) (U
 		case column == "og_image" && !ValidImageURL(v):
 			problems[column] = append(problems[column], models.Problem{Key: errImageURL})
 			continue
+		case (column == DataPrimaryParent || column == DataSchema) && owner.WrittenTo != WrittenToRecord:
+			if v != "" {
+				problems[column] = append(problems[column], models.Problem{Key: "golem15.seo::lang.api.record_only"})
+			}
+			continue
+		case column == DataPrimaryParent && v != "":
+			found := false
+			for _, opt := range s.ParentOptions(ctx, typ.Key, owner.ID, "") {
+				found = found || opt.Value == v
+			}
+			if !found {
+				problems[column] = append(problems[column], models.Problem{Key: "golem15.seo::lang.api.value_invalid"})
+				continue
+			}
+		case column == DataSchema:
+			stored, _, err := schema.Normalize(typ.Content.Kind, pageVariant(tx, typ.Key, owner.ID), v)
+			if err != nil {
+				problems[column] = append(problems[column], SchemaProblem(typ.Content.Kind, err))
+				continue
+			}
+			v = stored
 		}
 		values[column] = v
 	}
@@ -181,6 +206,9 @@ func (s *Service) SetURLSEO(ctx context.Context, tx *gorm.DB, in URLSEOWrite) (U
 		for _, column := range EntryColumns {
 			out[column] = EntryValue(e, column)
 		}
+		for _, column := range DataColumns {
+			out[column] = EntryValue(e, column)
+		}
 		return URLSEOResult{Owner: owner, Values: out}, nil
 	}
 	rule := models.Rule{URL: owner.URL, Match: models.MatchExact}