feat(12.1-02): password and form-only fields, rules per operation and preset

- pact.FormVirtualFields lists form fields that are not model columns: never
  bound, filled or projected; their values reach the Form hooks through
  cabana.VirtualFieldsFromContext when the field's context allows the operation
- type: password is a masked field that must be listed as virtual
- pact.FormRules supplies the rule set per operation and replaces the model's
  Rules() for admin saves; a rule on a virtual field sees the submitted value
- preset on a text field follows another text field on the create form
- SPA: PasswordField, preset handling in FormView, empty password left out of
  an update
- README, docs, OpenAPI document, TS types and dist updated

modules/cabana/extension.go

@@ -113,6 +113,12 @@ func compileExtension(pluginID string, cc *CompiledController, fsys fs.FS) error
 	for _, field := range cc.Form.Fields {
 		fields[field.Name] = field
 	}
+	if err := checkVirtualFields(cc, fields); err != nil {
+		return bootErr(pluginID, id, file, err)
+	}
+	if err := checkPresets(cc.Form.Fields); err != nil {
+		return bootErr(pluginID, id, file, err)
+	}
 	writable := map[string]bool{}
 	for _, field := range cc.Writable {
 		writable[field.Name] = true
@@ -147,6 +153,44 @@ func compileExtension(pluginID string, cc *CompiledController, fsys fs.FS) error
 	return nil
 }
 
+// virtualFieldTypes are the field types a controller may list through
+// pact.FormVirtualFields: the value is one scalar.
+var virtualFieldTypes = map[string]bool{
+	"password": true, "text": true, "textarea": true, "number": true,
+	"checkbox": true, "switch": true, "dropdown": true,
+}
+
+// checkVirtualFields checks the controller's pact.FormVirtualFields list
+// against the form: every `type: password` field must be listed (its value is
+// never a model column), and every listed name must be a field of the form
+// with a scalar type.
+func checkVirtualFields(cc *CompiledController, fields map[string]FormField) error {
+	for _, field := range cc.Form.Fields {
+		if field.Type == "password" && !cc.virtual[field.Name] {
+			return fmt.Errorf("field %s: type password needs the controller to list it in FormVirtualFields", field.Name)
+		}
+	}
+	src, ok := cc.Controller.(pact.FormVirtualFields)
+	if !ok || src == nil {
+		return nil
+	}
+	seen := map[string]bool{}
+	for _, name := range src.FormVirtualFields() {
+		if seen[name] {
+			return fmt.Errorf("FormVirtualFields lists field %s twice", name)
+		}
+		seen[name] = true
+		field, exists := fields[name]
+		if !exists {
+			return fmt.Errorf("FormVirtualFields: field %s is not a field of this form", name)
+		}
+		if !virtualFieldTypes[field.Type] {
+			return fmt.Errorf("FormVirtualFields: field %s has type %s (want password, text, textarea, number, checkbox, switch or dropdown)", name, field.Type)
+		}
+	}
+	return nil
+}
+
 // compilePartials reads and parses every partial the controller declares:
 // config_list.yaml headerPartial, config_form.yaml preview.headerPartial and
 // each `type: partial` field's path, all resolving to {ConfigDir}/_{name}.htm.