Fix/agentflow Add support for XML tag in markdown input and render markdown conditionally

[j-sanaa]

Ported #6061 and #6095 from legacy UI to agentflow

• added support for XML tag preservation — XML tags like are now preserved through TipTap's markdown round-trip instead of being stripped.
• Added functionality to conditionally configure link support based on the useMarkdown prop

Custom.XML.tags.mov

Limit.HTML.tags.mov

[gemini-code-assist]

Code Review

This pull request implements a system to preserve XML and HTML tags during TipTap's markdown serialization and deserialization processes. It introduces new utilities for escaping and unescaping tags, refactors existing editor helpers into a centralized xmlTagUtils.ts file, and updates the RichTextEditor and VariableInput components to utilize these utilities. Review feedback highlights opportunities to deduplicate content loading logic within the editor components and suggests seeking a more type-safe approach for the cache manager configuration in the server package.