Fetch O2M child records in web_read/web_search_read responses

When a view specification requests O2M fields (e.g., order_line on
sale.order), the response now includes the child records as an array
of dicts. Searches child model by inverse_field = parent_id, reads
requested sub-fields, and formats M2O/dates/nulls on children too.

This makes inline list views in form notebooks show actual data:
- Sale order lines (product, qty, price) in sale.order form
- Invoice lines in account.move form
- Any O2M field with specification in get_views response

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/server/web_methods.go

@@ -86,6 +86,9 @@ func handleWebSearchRead(env *orm.Environment, model string, params CallKWParams
 	// Format M2O fields as {id, display_name} when spec requests it
 	formatM2OFields(env, model, records, spec)
 
+	// Fetch O2M fields (child records) based on specification
+	formatO2MFields(env, model, records, spec)
+
 	// Format date/datetime fields to Odoo's expected string format
 	formatDateFields(model, records)
 
@@ -133,6 +136,9 @@ func handleWebRead(env *orm.Environment, model string, params CallKWParams) (int
 
 	formatM2OFields(env, model, records, spec)
 
+	// Fetch O2M fields (child records) based on specification
+	formatO2MFields(env, model, records, spec)
+
 	// Format date/datetime fields to Odoo's expected string format
 	formatDateFields(model, records)
 
@@ -145,6 +151,87 @@ func handleWebRead(env *orm.Environment, model string, params CallKWParams) (int
 	return records, nil
 }
 
+// formatO2MFields fetches One2many child records and adds them to the response.
+// Mirrors: odoo/addons/web/models/models.py web_read() O2M handling
+func formatO2MFields(env *orm.Environment, modelName string, records []orm.Values, spec map[string]interface{}) {
+	m := orm.Registry.Get(modelName)
+	if m == nil || spec == nil {
+		return
+	}
+
+	for fieldName, fieldSpec := range spec {
+		f := m.GetField(fieldName)
+		if f == nil || f.Type != orm.TypeOne2many {
+			continue
+		}
+
+		// Check if spec requests sub-fields
+		specMap, ok := fieldSpec.(map[string]interface{})
+		if !ok {
+			continue
+		}
+		subFieldsSpec, _ := specMap["fields"].(map[string]interface{})
+
+		// Determine which fields to read from child model
+		var childFields []string
+		if len(subFieldsSpec) > 0 {
+			childFields = []string{"id"}
+			for name := range subFieldsSpec {
+				if name != "id" {
+					childFields = append(childFields, name)
+				}
+			}
+		}
+
+		comodel := f.Comodel
+		inverseField := f.InverseField
+		if comodel == "" || inverseField == "" {
+			continue
+		}
+
+		for _, rec := range records {
+			parentID, ok := rec["id"].(int64)
+			if !ok {
+				if pid, ok := rec["id"].(int32); ok {
+					parentID = int64(pid)
+				}
+			}
+			if parentID == 0 {
+				rec[fieldName] = []interface{}{}
+				continue
+			}
+
+			// Search child records where inverse_field = parent_id
+			childRS := env.Model(comodel)
+			domain := orm.And(orm.Leaf(inverseField, "=", parentID))
+			found, err := childRS.Search(domain, orm.SearchOpts{Limit: 200})
+			if err != nil || found.IsEmpty() {
+				rec[fieldName] = []interface{}{}
+				continue
+			}
+
+			// Read child records
+			childRecords, err := found.Read(childFields)
+			if err != nil {
+				rec[fieldName] = []interface{}{}
+				continue
+			}
+
+			// Format child records (M2O fields, dates, nulls)
+			formatM2OFields(env, comodel, childRecords, subFieldsSpec)
+			formatDateFields(comodel, childRecords)
+			normalizeNullFields(comodel, childRecords)
+
+			// Convert to []interface{} for JSON
+			lines := make([]interface{}, len(childRecords))
+			for i, cr := range childRecords {
+				lines[i] = cr
+			}
+			rec[fieldName] = lines
+		}
+	}
+}
+
 // specToFields extracts field names from a specification dict.
 // {"name": {}, "partner_id": {"fields": {"display_name": {}}}} → ["name", "partner_id"]
 func specToFields(spec map[string]interface{}) []string {