fix(vscode-ext): prevent autosave from opening a Save File dialog on every edit - #3781

Problem

Fixes #3768. Editing any .docx in the SuperDoc VS Code extension pops a browser "Save File" dialog on essentially every edit (the ~1s debounced autosave and Cmd/Ctrl+S both trigger it), which makes real editing unusable.

Root cause

The webview autosave calls editor.export({ format: 'docx' }). SuperDoc's export() defaults triggerDownload: true, and for a single docx blob that path calls createDownload(...) → window.showSaveFilePicker, opening the dialog. (format is also not a recognized export() option — the correct key is exportType.)

Fix

Pass triggerDownload: false (and the correct exportType: ['docx']) so export() returns the Blob directly — exactly what the blob.arrayBuffer() → postMessage save path consumes. No dialog; silent autosave-to-disk keeps working.

// apps/vscode-ext/webview/main.js
- const blob = await editor.export({ format: 'docx' });
+ const blob = await editor.export({ exportType: ['docx'], triggerDownload: false });