fix(vscode): update Flyde imports when files move

[huipan18]

Summary

This PR addresses issue #112, where moving an imported Flyde file causes its existing references to break.

Changes

• Register a VS Code onWillRenameFiles handler to detect file and folder moves.
• Recalculate relative paths for file-backed node references.
• Handle references inside nested inline visual nodes.
• Preserve unrelated package-backed references.

Validation

• Successfully compiled the VS Code extension.
• Reproduced the original issue using Main.flyde and Macro.flyde.ts.
• Performed an initial manual test of the updated file-move behavior.

Related issue

Addresses #112.

This is an independently developed implementation. I am aware that PR #275 also addresses this issue.