fix(theme): improve SSR compatibility

[SoonIter]

Summary

• Replace useLayoutEffect with useEffect in useStorageValue to avoid SSR warnings
• Add SSR guard (typeof window check) in useStorageValue
• Remove global renderCountForTocUpdate counter in PageTabs that causes hydration mismatch

Background

useStorageValue issues

The useStorageValue hook had two SSR compatibility issues:

1. Used useLayoutEffect which causes warnings during SSR
2. Accessed localStorage without checking if window is defined

PageTabs hydration mismatch

The PageTabs component used a global counter renderCountForTocUpdate that was incremented on every render. This counter was used to conditionally render a hidden <h2> element for TOC updates. Since the counter value could differ between server and client renders, this caused hydration mismatches.

Test plan

• Verify no SSR warnings in console during build
• Verify tabs with groupId work correctly (state persisted in localStorage)
• Verify PageTabs component renders correctly without hydration errors

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[Copilot]

Pull request overview

This PR improves SSR (Server-Side Rendering) compatibility by fixing issues in the useStorageValue hook and PageTabs component. The changes address SSR warnings from useLayoutEffect usage, add browser environment guards, and eliminate a hydration mismatch caused by a global render counter.

Key changes:

• Replace useLayoutEffect with useEffect and add SSR guard in useStorageValue hook
• Remove global renderCountForTocUpdate counter and conditional TOC update logic from PageTabs component

Reviewed changes

Copilot reviewed 1 out of 1 changed files in this pull request and generated no comments.

File	Description
packages/core/src/theme/logic/useStorageValue.ts	Migrates from useLayoutEffect to useEffect with SSR guard for localStorage access, updates dependency array to include key
packages/core/src/theme/components/PageTabs/index.tsx	Removes global counter and conditional hidden <h2> rendering that caused hydration mismatches

Comments suppressed due to low confidence (1)

packages/core/src/theme/logic/useStorageValue.ts:45

• The setValue callback accesses localStorage and dispatchEvent without checking if window is defined. This will cause errors during SSR when this function is called. Add a guard to check typeof window !== 'undefined' before accessing browser APIs.

  const setValue = useCallback(
    (value: T) => {
      const next = value;
      if (next == null) {
        localStorage.removeItem(key);
      } else {
        localStorage.setItem(key, next.toString());
      }
      setValueInternal(next);
      dispatchEvent(
        // send custom event to communicate within same page
        // importantly this should not be a StorageEvent since those cannot
        // be constructed with a non-built-in storage area
        new CustomEvent<{ key: string; newValue: T }>(SYNC_STORAGE_EVENT_NAME, {
          detail: {
            key,
            newValue: next,
          },
        }),
      );
    },
    [key],
  );

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[github-actions]

Rsdoctor Bundle Diff Analysis

Found 3 projects in monorepo, 1 project with changes.

📊 Quick Summary

Project	Total Size	Change
node	9.3 MB	0
node_md	1.1 MB	0
web	15.1 MB	+23.0 B (0.0%)

📋 Detailed Reports (Click to expand)

📁 web

Path: website/doc_build/diff-rsdoctor/web/rsdoctor-data.json

📌 Baseline Commit: c03d863a6b | PR: #2927

Metric	Current	Baseline	Change
📊 Total Size	15.1 MB	15.1 MB	+23.0 B (0.0%)
📄 JavaScript	14.4 MB	14.4 MB	+23.0 B (0.0%)
🎨 CSS	115.4 KB	115.4 KB	0
🌐 HTML	0 B	0 B	0
📁 Other Assets	526.5 KB	526.5 KB	0

📦 Download Diff Report: web Bundle Diff

Generated by Rsdoctor GitHub Action