test(studio): lock the split view's server render and hydration

[Deodat-Lawson]

Summary

• Adds regression tests for a server-render crash in StudioSplitView. Since feat(studio): split the workspace centre into columns of tabs #409 it built its per-tab portal hosts with document.createElement during render, so any server render threw ReferenceError: document is not defined. GET /dev/studio-tabs returned 500 on next dev.
• The fix itself is already on main. This PR started as that fix. In the meantime main fixed the same crash independently in 76ed6c3 (split panes): a mounted flag set in useEffect now gates the memoised PanePortals. When resolving conflicts I took main's component as-is, so there is one fix, not two. This PR now changes no source code.
• Main had no server-render coverage, so the tests stay:
  • __tests__/StudioSplitView.ssr.test.tsx (new, @jest-environment node): renderToString succeeds with no document, draws both panes' strips and leaves pane content out of the markup.
  • __tests__/StudioSplitView.test.tsx (one new case): server-renders, hydrateRoots the markup with nothing logged, then moves Chat to the other pane and checks it's the same element with its draft and a single mount.

Related

Follow-up to #409. Covers the server-render path of the fix in 76ed6c3.

Checklist

• pnpm check passes (lint + typecheck): not run repo-wide. tsc --noEmit for apps/web and eslint on the touched files both exit 0.
• pnpm --filter @launchstack/web test passes: ran the documents/_workspace suite only (34 suites, 326 tests, all pass).
• Changeset added (if packages/core/ changed): N/A, tests only
• New env vars documented: N/A, none
• UI changes exercised in a browser: N/A, no UI change. /dev/studio-tabs returns 200 on the merged tree.
• Docs updated if behavior changed: N/A

Testing

• The tests guard main's fix: with main's {mounted && <PanePortals … />} gate temporarily removed, all three new tests fail; with it in place, all 20 StudioSplitView tests pass.
• Against the pre-feat(studio): split the workspace centre into columns of tabs #409-follow-up code (the original bug), the same three tests also failed. That was verified before the merge.
• Dev route: curl -s -o /dev/null -w "%{http_code}" http://localhost:3011/dev/studio-tabs returns 200 on the merged branch.

Notes for reviewers

• The product route was never exposed. WorkspaceShell renders <LoadingPage /> until the Better Auth session resolves, and that never happens on the server. Only the auth-free dev harness crashed. These tests make the component's own SSR safety explicit instead of relying on that check.
• Test quirks:
  • The SSR test is its own file because jsdom supplies a document and would hide this class of bug.
  • In the jsdom file, react-dom/server.node is imported because the browser build needs a TextEncoder that jsdom lacks.
  • Jest runs react@18.3.1, whose server renderer warns "useLayoutEffect does nothing on the server"; the app runs Next's bundled React 19.2 canary, which doesn't. Both tests filter exactly that message and fail on anything else logged.
• A possible refinement to main's fix, not done here. Main sets mounted in a useEffect, so on a plain client-side mount (the product path) the first commit has no pane content. Panes appear a frame later. This branch originally used useSyncExternalStore(noop, () => true, () => false), which is false on the server and during hydration but true on a client-side mount, so panes render in the first commit. The difference is one frame on first mount; happy to follow up if wanted.

🤖 Generated with Claude Code

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Note

Low Risk
Test-only changes that lock in SSR/hydration behavior for the documents workspace split view, with no production logic in this diff.

Overview
Adds regression tests so StudioSplitView can be server-rendered without touching document, and so client hydration still preserves pane DOM/state when tabs move between columns.

A new Node/Jest SSR suite (StudioSplitView.ssr.test.tsx) runs renderToString with no document, asserts render completes without console errors (aside from filtered React 18 useLayoutEffect warnings), and checks the HTML includes the tab strips but not pane body content.

The existing jsdom suite is refactored with a shared viewOf helper, and gains a hydrate-then-move case: server markup is injected, hydrateRoot runs cleanly, pane content appears after hydration, and moving Chat to another column keeps the same element, draft value, and mount count.

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-23T04:01:06.057261Z	addb2ca	PR opened

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