feat(server): improve markdown parse (#14580)

#### PR Dependency Tree


* **PR #14580** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Markdown conversion now reports lists of known-unsupported and unknown
block identifiers encountered during parsing, and separates them from
the main markdown output.

* **Bug Fixes**
  * Improved error handling and logging around markdown parsing.

* **Tests**
* Updated tests and snapshots to reflect the new block-list fields and
the adjusted markdown output.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/native/src/doc.rs

@@ -9,6 +9,8 @@ use napi_derive::napi;
 pub struct NativeMarkdownResult {
   pub title: String,
   pub markdown: String,
+  pub known_unsupported_blocks: Vec<String>,
+  pub unknown_blocks: Vec<String>,
 }
 
 impl From<MarkdownResult> for NativeMarkdownResult {
@@ -16,6 +18,8 @@ impl From<MarkdownResult> for NativeMarkdownResult {
     Self {
       title: result.title,
       markdown: result.markdown,
+      known_unsupported_blocks: result.known_unsupported_blocks,
+      unknown_blocks: result.unknown_blocks,
     }
   }
 }