feat: add four-phase role description (identity/prepare/execute/report)

- Extend RoleDefinition with identity, prepare, execute, report fields
- Make systemPrompt optional (nullable) for four-phase workflows
- Update ROLE_DEFINITION JSON Schema (all new fields optional)
- Update validate.ts to accept new fields
- Update workflow.ts to strip null fields before CAS storage
- Update thread read to prefer identity over systemPrompt
- Add --version flag to uwf CLI
- Bump all packages to 0.5.0

Refs #359

packages/cli-workflow/src/validate.ts

@@ -16,9 +16,17 @@ function isRoleDefinition(value: unknown): boolean {
   }
   const outputSchema = value.outputSchema;
   const schemaOk = isRecord(outputSchema) && typeof outputSchema.type === "string";
-  return (
-    typeof value.description === "string" && typeof value.systemPrompt === "string" && schemaOk
-  );
+  const hasSystemPrompt =
+    value.systemPrompt === undefined || value.systemPrompt === null || typeof value.systemPrompt === "string";
+  const hasIdentity =
+    value.identity === undefined || value.identity === null || typeof value.identity === "string";
+  const hasPrepare =
+    value.prepare === undefined || value.prepare === null || typeof value.prepare === "string";
+  const hasExecute =
+    value.execute === undefined || value.execute === null || typeof value.execute === "string";
+  const hasReport =
+    value.report === undefined || value.report === null || typeof value.report === "string";
+  return typeof value.description === "string" && hasSystemPrompt && hasIdentity && hasPrepare && hasExecute && hasReport && schemaOk;
 }
 
 function isConditionDefinition(value: unknown): boolean {