fix(super-editor): rethrow export docx errors

[xy200303]

Summary

• Re-throw normalized Editor.exportDocx() errors after preserving the existing exception event and console logging.
• Remove undefined from the internal implementation return union.
• Add a regression test that verifies failed converter.exportToDocx calls reject to the caller.

Verification

• pnpm test:editor -- src/editors/v1/tests/export/exportDocx.errors.test.js
• pnpm test:editor -- src/editors/v1/tests/export/exportDocx.errors.test.js src/editors/v1/tests/export/exportDocx.commentsFallback.test.js
• pnpm --prefix packages/super-editor run types:check (fails: existing unresolved @superdoc/font-system declarations and broad pre-existing JS/TS errors)

Closes #3579

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.75000% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
packages/superdoc/src/core/SuperDoc.ts	93.75%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!

[caio-pizzol]

@xy200303 thanks for the fix. I pushed a follow-up commit that covers the SuperDoc wrapper path and avoids duplicate export exception events.

The added coverage checks that a rejected editor export falls back to the original DOCX data, sibling documents still export, and a bridged editor exception does not cause a second wrapper exception.

I only ran git diff --check; local unit tests were not run because this repo asks us not to run them locally. CI is queued.

lgtm.