chore: migrate @uncaged/json-cas to @ocas/core, @uncaged/json-cas-fs to @ocas/fs

- Replace all package.json dependencies
- Update all imports across 7 packages + scripts
- cas_ref → ocas_ref in schema definitions
- listByType() adapted for ListEntry[] return type
- Update CLAUDE.md references

Fixes #585

packages/workflow-util-agent/__tests__/frontmatter-fast-path.test.ts

@@ -1,4 +1,4 @@
-import { createMemoryStore, putSchema } from "@uncaged/json-cas";
+import { createMemoryStore, putSchema } from "@ocas/core";
 import { describe, expect, test } from "vitest";
 
 import { tryFrontmatterFastPath } from "../src/frontmatter.js";