fix: accept omitted condition in fallback transitions

Fallback transitions (last entry in graph node) omit the condition
field in YAML, resulting in undefined instead of null. The validator
and materializer now handle this:

- validate.ts: accept undefined as valid condition value
- workflow.ts: normalizeGraph() coerces undefined → null before CAS put

This was broken by the graph fallback pattern introduced in #370.

packages/cli-workflow/src/commands/workflow.ts

@@ -2,7 +2,12 @@ import { readFile } from "node:fs/promises";
 
 import type { JSONSchema } from "@uncaged/json-cas";
 import { putSchema, validate } from "@uncaged/json-cas";
-import type { CasRef, RoleDefinition, WorkflowPayload } from "@uncaged/workflow-protocol";
+import type {
+  CasRef,
+  RoleDefinition,
+  Transition,
+  WorkflowPayload,
+} from "@uncaged/workflow-protocol";
 import { parse } from "yaml";
 
 import {
@@ -46,6 +51,18 @@ function isJsonSchema(value: unknown): value is JSONSchema {
   return typeof value === "object" && value !== null && !Array.isArray(value);
 }
 
+/** Normalize graph transitions: ensure condition is null (not undefined) for fallback entries. */
+function normalizeGraph(graph: Record<string, Transition[]>): Record<string, Transition[]> {
+  const result: Record<string, Transition[]> = {};
+  for (const [node, transitions] of Object.entries(graph)) {
+    result[node] = transitions.map((t) => ({
+      role: t.role,
+      condition: t.condition ?? null,
+    }));
+  }
+  return result;
+}
+
 async function resolveFrontmatterRef(
   uwf: UwfStore,
   roleName: string,
@@ -84,7 +101,7 @@ export async function materializeWorkflowPayload(
     description: raw.description,
     roles,
     conditions: raw.conditions,
-    graph: raw.graph,
+    graph: normalizeGraph(raw.graph),
   };
 }
 

packages/cli-workflow/src/validate.ts

@@ -42,7 +42,10 @@ function isTransition(value: unknown): boolean {
     return false;
   }
   const condition = value.condition;
-  return typeof value.role === "string" && (condition === null || typeof condition === "string");
+  return (
+    typeof value.role === "string" &&
+    (condition === null || condition === undefined || typeof condition === "string")
+  );
 }
 
 function isStringRecord(value: unknown, itemCheck: (item: unknown) => boolean): boolean {