vscode.provideDocumentSemanticTokens returns null when using native preview with built-in TS extension disabled

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### 🔎 Search Terms

vscode.provideDocumentSemanticTokens

### 🕗 Version & Regression Information

- `textDocument/semanticTokens/full` are computed as shown in output panel.
- editor renders semantic highlighting correctly
- But `vscode.provideDocumentSemanticTokens` returns null/undefined when called from another extension
- other language ext that register `DocumentSemanticTokensProvider` works though. even `pwsh`

### ⏯ Playground Link

_No response_

### 💻 Code

```ts
// Your code here
```

### 🙁 Actual behavior

inconsistent sem token return

### 🙂 Expected behavior

should be consistent in output panel and when called from another ext

### Additional information about the issue

_No response_

Start by reproducing the issue with the native preview enabled and the built-in TypeScript extension disabled, comparing the output panel's textDocument/semanticTokens/full result with vscode.provideDocumentSemanticTokens from another extension. The issue is done when the API behavior is consistent with the output panel for TypeScript, with regression coverage or a documented limitation if the behavior is intentional.

Written by the indexing model from the issue text.