@mermaid-js/[email protected]: Langium v4 upgrade @mermaid-js/[email protected]

We've shipped the parser on Langium v4, which means better type safety and faster parsing under the hood. Fair warning: if you're consuming this package, you'll need TypeScript 5.8+ and the generated AST types moved from `` to `.$type`. Bonus: this kills some gnarly lodash CVEs in the dependency tree.