fix(query): surface traced diagnostics at main callsites

[GeronimoCastano]

Summary

When Typst reports an error inside an imported module or package, Tinymist assigns the primary LSP diagnostic to the internal source span and sends the user callsite through relatedInformation.

VS Code lists the diagnostic in the Problems panel, but Error Lens cannot display it beside the call that caused the error. Neovim clients have the same problem when they do not expose relatedInformation.

This change uses the outermost trace span in the main document as the displayed diagnostic location when the original error comes from another file. It keeps the original source location in relatedInformation with the message diagnostic originated here.

Diagnostics that originate in the main document keep their current location.

Tests

Added diagnostic fixtures covering:

• an error raised in an imported file with a callsite in the main document;
• an error raised directly in the main document.

Ran:

• cargo test -p tinymist-query
• cargo build -p tinymist-cli --release

Addresses #1870.