fix(validate): support enum-based multi-exit and upgrade json-cas to 0.5.3

Two fixes for 'uwf thread start solve-issue' failures:

1. json-cas 0.5.2 (npm) was missing oneOf in ALLOWED_SCHEMA_KEYS.
   Published json-cas 0.5.3 with the fix, bumped all packages to ^0.5.3.

2. Semantic validator only recognized oneOf-based multi-exit schemas.
   Roles using $status with enum (e.g. enum: [approved, rejected]) were
   incorrectly treated as single-exit. Added isEnumMultiExit() support.

Changes:
- validate-semantic.ts: isEnumMultiExit(), getEnumStatuses(), checkSingleExitMustache()
- All package.json: @uncaged/json-cas ^0.5.2 → ^0.5.3
- validate-semantic.test.ts: 5 new enum multi-exit tests (Suite 3b)
- solve-issue-tea-worktree.test.ts: updated for current workflow structure

小橘 🍊

packages/workflow-agent-builtin/package.json

@@ -22,7 +22,7 @@
     "test:ci": "bun test"
   },
   "dependencies": {
-    "@uncaged/json-cas": "^0.5.2",
+    "@uncaged/json-cas": "^0.5.3",
     "@uncaged/workflow-util-agent": "workspace:^",
     "@uncaged/workflow-util": "workspace:^"
   },