Feat v0.9.5 typed forms SDK primitive

Extract typed form system from models/workflow.go into standalone
server/forms/ package. Any package can now declare and validate
forms, not just workflow stages.

- New server/forms/ package (types + validation + condition evaluator)
- REST POST /api/v1/forms/validate endpoint
- Starlark forms.validate(template, data) module
- Frontend sw.forms.render(), .validate(), .validateRemote()
- Manifest form_template accepted at package level
- 16 new tests (12 forms + 4 Starlark module)

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

server/sandbox/forms_module.go

@@ -0,0 +1,86 @@
+package sandbox
+
+// forms_module.go
+//
+// Starlark forms module — validates form data against typed form templates.
+// Gated by the forms.validate extension permission.
+//
+// Starlark API:
+//   result = forms.validate(template, data)
+//   # result["valid"]  → True/False
+//   # result["errors"] → [{"key": "...", "message": "..."}, ...]
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"go.starlark.net/starlark"
+	"go.starlark.net/starlarkstruct"
+
+	"armature/forms"
+)
+
+// BuildFormsModule creates the "forms" Starlark module.
+// Requires the forms.validate permission.
+func BuildFormsModule(_ context.Context) *starlarkstruct.Module {
+	return MakeModule("forms", starlark.StringDict{
+		"validate": starlark.NewBuiltin("forms.validate", formsValidateBuiltin()),
+	})
+}
+
+func formsValidateBuiltin() func(*starlark.Thread, *starlark.Builtin, starlark.Tuple, []starlark.Tuple) (starlark.Value, error) {
+	return func(_ *starlark.Thread, b *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
+		var templateVal, dataVal starlark.Value
+		if err := starlark.UnpackPositionalArgs(b.Name(), args, kwargs, 2, &templateVal, &dataVal); err != nil {
+			return nil, err
+		}
+
+		// Convert template dict → Go map → JSON → TypedFormTemplate
+		templateDict, ok := templateVal.(*starlark.Dict)
+		if !ok {
+			return nil, fmt.Errorf("forms.validate: template must be a dict, got %s", templateVal.Type())
+		}
+		templateMap := DictToMap(templateDict)
+		templateJSON, err := json.Marshal(templateMap)
+		if err != nil {
+			return nil, fmt.Errorf("forms.validate: failed to marshal template: %w", err)
+		}
+
+		tpl := forms.ParseTypedFormTemplate(json.RawMessage(templateJSON))
+		if tpl == nil {
+			return nil, fmt.Errorf("forms.validate: template is invalid or empty")
+		}
+
+		// Convert data dict → Go map
+		dataDict, ok := dataVal.(*starlark.Dict)
+		if !ok {
+			return nil, fmt.Errorf("forms.validate: data must be a dict, got %s", dataVal.Type())
+		}
+		dataMap := DictToMap(dataDict)
+
+		// Coerce to map[string]interface{}
+		data := make(map[string]interface{}, len(dataMap))
+		for k, v := range dataMap {
+			data[k] = v
+		}
+
+		// Validate
+		errs := forms.ValidateFormData(tpl, data)
+
+		// Build result dict
+		errList := make([]starlark.Value, len(errs))
+		for i, e := range errs {
+			d := starlark.NewDict(2)
+			_ = d.SetKey(starlark.String("key"), starlark.String(e.Key))
+			_ = d.SetKey(starlark.String("message"), starlark.String(e.Message))
+			errList[i] = d
+		}
+
+		result := starlark.NewDict(2)
+		_ = result.SetKey(starlark.String("valid"), starlark.Bool(len(errs) == 0))
+		_ = result.SetKey(starlark.String("errors"), starlark.NewList(errList))
+
+		return result, nil
+	}
+}