feat(09-03): compile ordered Winter form schemas

- Strict config_form and fields documents keep source order and JSON scalar types
- Unknown keys, partials, path escape, and a mismatched modelClass fail activation with plugin context
- List-only controllers still activate when config_form.yaml is absent

cabana/schema_types.go

@@ -0,0 +1,71 @@
+package cabana
+
+import "encoding/json"
+
+// FormSchema is the locale-neutral form contract compiled once at boot.
+// Display strings stay as source keys until a request localizes a copy.
+type FormSchema struct {
+	Name       string      `json:"name,omitempty"`
+	ModelClass string      `json:"modelClass,omitempty"`
+	Fields     []FormField `json:"fields"`
+}
+
+// FormField is one Winter field in source order. JSON keys keep Winter spelling.
+type FormField struct {
+	Name        string                `json:"name"`
+	Type        string                `json:"type"`
+	Label       string                `json:"label,omitempty"`
+	Comment     string                `json:"comment,omitempty"`
+	Span        string                `json:"span,omitempty"`
+	Tab         string                `json:"tab,omitempty"`
+	Size        string                `json:"size,omitempty"`
+	Context     *fieldContext         `json:"context,omitempty"`
+	NameFrom    string                `json:"nameFrom,omitempty"`
+	EmptyOption string                `json:"emptyOption,omitempty"`
+	Relation    string                `json:"relation,omitempty"`
+	Required    bool                  `json:"required,omitempty"`
+	Default     *jsonScalar           `json:"default,omitempty"`
+	Attributes  map[string]jsonScalar `json:"attributes,omitempty"`
+	Options     []FormOption          `json:"options,omitempty"`
+
+	optionsMethod string
+}
+
+// FormOption is one dropdown choice. Value keeps the YAML scalar's JSON type.
+type FormOption struct {
+	Value jsonScalar `json:"value"`
+	Label string     `json:"label"`
+}
+
+// jsonScalar is a JSON scalar that still emits false, 0, and empty string.
+type jsonScalar struct {
+	raw json.RawMessage
+}
+
+func (s jsonScalar) MarshalJSON() ([]byte, error) {
+	if len(s.raw) == 0 {
+		return []byte("null"), nil
+	}
+	return s.raw, nil
+}
+
+// fieldContext preserves a single Winter context string or a source-ordered list.
+type fieldContext struct {
+	single bool
+	values []string
+}
+
+func (c fieldContext) MarshalJSON() ([]byte, error) {
+	if c.single {
+		text := ""
+		if len(c.values) > 0 {
+			text = c.values[0]
+		}
+		return json.Marshal(text)
+	}
+	values := c.values
+	if values == nil {
+		values = []string{}
+	}
+	return json.Marshal(values)
+}