fix(preview): increase whitespace padding to 200 chars for Gmail

[mvanhorn]

Summary

Increases PREVIEW_MAX_LENGTH from 150 to 200 in the <Preview> component. Gmail shows up to 200 characters of preview text, so the previous 150-character limit left a gap where body content could bleed through into the email preview snippet.

Changes

• packages/preview/src/preview.tsx: Changed PREVIEW_MAX_LENGTH constant from 150 to 200
• packages/preview/src/preview.spec.tsx: Updated inline snapshots and assertions to match the new limit

The renderWhiteSpace() function and substring() truncation both reference this constant, so all behavior updates automatically.

Testing

• All 5 existing tests pass after snapshot update
• Verified the whitespace padding div now contains 200 repetitions for short text
• Long text (>200 chars) still truncates correctly with no whitespace padding

Fixes #2268

This contribution was developed with AI assistance (Claude Code).

---

Summary by cubic

Pads email preview text to 200 chars in @react-email/preview to match Gmail and prevent body content from bleeding into snippets. Updates the Preview component limit and refreshes related snapshots; long text still truncates.

• Changes: set PREVIEW_MAX_LENGTH to 200 in packages/react-email/src/components/preview/preview.tsx; updated inline snapshots in packages/react-email preview tests, CLI export test, and packages/ui test; added a changeset for @react-email/preview.

^{Written for commit aa54282. Summary will update on new commits. Review in cubic}

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Latest commit: aa54282

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[cubic-dev-ai]

No issues found across 2 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@react-email/preview@3100

npm i https://pkg.pr.new/@react-email/preview-server@3100

npm i https://pkg.pr.new/react-email@3100

commit: f1f6f04

[gabrielmfern]

can you confirm this doesn't include extra whitespaces for other email clients?

[mvanhorn]

The whitespace padding uses zero-width Unicode characters (U+200C, U+200D, U+200E, U+200F, U+FEFF) in a hidden div with display:none. These characters are invisible across all email clients - they're the same characters already used at the 150-char limit, just extended to 200. Tested rendering in the preview server and the output is identical except for the padding count. No visible whitespace is added to the email body.

[mvanhorn]

Hey @gabrielmfern, gentle ping on this -- the answer to your March question is in the comment above (zero-width Unicode chars in a display:none div, no visible whitespace added to the email body). Happy to rebase against canary if you want to take another look.

[dielduarte]

Hey @mvanhorn, sorry for our delay on this. Can you please do a rebase? That would indeed help move this one to the finish line! thanks!

[mvanhorn]

Rebased onto canary (aa54282). All 4 commits replayed cleanly, no conflicts.

Ready for another look whenever you have a minute.