fix(files): stop markdown reflow on open by matching placeholder wrapping to the editor

[waleedlatif1]

Summary

• Fixes the flicker where a line's word-wrap shifts on first open/refresh of a markdown file (e.g. "…shook only a little" starts on one line, then "little" jumps down as the doc settles).
• Root cause: collaborative files render a static placeholderHtml while the Yjs doc seeds, then swap to the live TipTap editor. The placeholder was .rich-markdown-prose only (browser-default white-space: normal), but the live editable is .ProseMirror.rich-markdown-prose, and prosemirror-view sets white-space: break-spaces and disables ligatures on .ProseMirror. Different wrapping model → identical text wraps at a different point → the visible re-wrap on the swap.
• Fix: give the placeholder the same ProseMirror class as the live editable, so both share the exact base text layout and wrap identically. One class added; no width/scrollbar/font changes.

Type of Change

• Bug fix

Testing

• Traced empirically, no guesswork: confirmed prosemirror-view/style/prosemirror.css sets white-space: break-spaces + font-variant-ligatures: none on .ProseMirror, and the placeholder lacked both. Both render sites already share width (max-w-[48rem] px-8), ruling out container width; ruled out scrollbar (macOS overlay scrollbars take no layout width) and font-swap (the bug repros on refresh with the font cached).
• Cross-checked prior art (TipTap docs/issues + inkeep/open-knowledge): inkeep's warm-HTML fallback avoids swap reflow precisely by reusing the live editor's exact classes — this mirrors that. No UX downside: the placeholder was already read-only; only its wrap model now matches the editor.
• Visual confirmation on staging recommended after deploy.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Aug 5, 2026 6:01am

[cursor]

PR Summary

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[greptile-apps]

Greptile Summary

This PR adds the ProseMirror class to the collaborative markdown placeholder so its whitespace and ligature behavior matches the live editor during document seeding.

• Aligns placeholder and editor text-wrapping behavior.
• Updates the inline comment to document why the class is required.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The placeholder receives the intended ProseMirror text-layout styles while the hidden live editor continues to seed normally, and no current selector or interaction path is disrupted by the additional class.

Important Files Changed

Filename	Overview
apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/rich-markdown-editor/rich-markdown-editor.tsx	Adds the live editor’s base ProseMirror styling class to the temporary read-only placeholder; no actionable regression was identified.

_{Reviews (1): Last reviewed commit: "fix(files): stop markdown reflow on open..." | Re-trigger Greptile}