feat(util): create @uncaged/workflow-util package

Extract pure utility functions from workflow/src/util/ into standalone package.
Types (Result, ok, err) now come from @uncaged/workflow-protocol.

Contains: base32 encoding, ULID generation, structured logger,
storage-root helpers, refs-field normalization.

Ref: #143, closes #145

packages/workflow-util/package.json

@@ -0,0 +1,17 @@
+{
+  "name": "@uncaged/workflow-util",
+  "version": "0.1.0",
+  "type": "module",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./src/index.ts"
+    }
+  },
+  "dependencies": {
+    "@uncaged/workflow-protocol": "workspace:*"
+  },
+  "devDependencies": {
+    "typescript": "^5.8.3"
+  }
+}