Run workflow stages with finish_stage handoffs and lead signals

internal/workflow/file.go

@@ -12,7 +12,7 @@ import (
 	"g.fc.run/misc/byre/internal/api"
 )
 
-var keyOrder = []string{"description", "stages", "name", "vendor", "model", "prompt"}
+var keyOrder = []string{"description", "stages", "name", "model", "prompt"}
 
 func Parse(data []byte) (api.WorkflowDefinition, error) {
 	raw := any(nil)

internal/workflow/workflow.go

@@ -62,13 +62,8 @@ func Validate(def api.WorkflowDefinition) error {
 		}
 		seen[s.Name] = true
 
-		switch {
-		case !s.Vendor.Valid():
-			problems = append(problems, fmt.Sprintf("%s: vendor must be claude or codex, not %q", where, s.Vendor))
-		case strings.TrimSpace(s.Model) == "":
+		if strings.TrimSpace(s.Model) == "" {
 			problems = append(problems, fmt.Sprintf("%s: model is required", where))
-		case string(VendorOf(s.Model)) != string(s.Vendor):
-			problems = append(problems, fmt.Sprintf("%s: %s is a %s model, not %s", where, s.Model, VendorOf(s.Model), s.Vendor))
 		}
 
 		if strings.TrimSpace(s.Prompt) == "" {