⚡ Bolt: Prevent redundant DOM updates on initial i18n load

[seonghobae]

💡 What:

Optimized the setLanguage function in i18n.js to cache DOM node queries (querySelectorAll, querySelector) and verify if the requested language text actually differs before updating the DOM's textContent or attributes.

🎯 Why:

The initial setLanguage call redundantly selected every translatable node on the page and updated its text content to the default Korean language. However, the HTML markup is already localized in Korean. Thus, the script initiated expensive, unnecessary blocking main thread work, triggering layout and paint re-calculations for content that didn't change.

📊 Impact:

• Reduces Main Thread Blocking: Completely eliminates initial DOM updates for the default language.
• Minimizes Repaints: Changing language now scales effectively as only the modified nodes trigger a re-render.
• Reduces DOM Queries: Caching elements prevents repetitive, expensive tree parsing on every button click.

🔬 Measurement:

Start the local server (python3 -m http.server 4173). Visiting the index without parameters performs almost zero DOM updates compared to before. Clicking the EN and KO buttons still translates correctly, visually verified through Playwright traces and logs.

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PR created automatically by Jules for task 1024467495292710943 started by @seonghobae

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[github-actions]

OpenCode Review Overview

• Head SHA: d6df237202682fe117cf20f9c461d6dc313e6585
• Workflow run: 27873923247
• Workflow attempt: 1
• Gate result: APPROVE (exit 0)

[opencode-agent]

OpenCode Agent approved this PR.

The changes optimize i18n DOM updates by adding caching and equality checks. The implementation correctly handles all edge cases and maintains functionality while reducing unnecessary layout operations. No security or regression risks found.

• Result: APPROVE
• Reason: Performance improvements with proper safety checks
• Head SHA: d6df237202682fe117cf20f9c461d6dc313e6585
• Workflow run: 27873923247
• Workflow attempt: 1