Migrate comment system from Utterances to Giscus

[Copilot]

• Fix TypeScript compilation error in HtmlLangUpdater.tsx
  • Added null check for locale from getLocaleFromPathname
  • Use default locale (i18n.defaultLocale) when pathname doesn't contain a valid locale
  • Import i18n types to access defaultLocale constant

TypeScript Error Fixed

The error occurred because getLocaleFromPathname returns Locale | null, but document.documentElement.lang expects a string. Fixed by using the nullish coalescing operator (??) to fallback to i18n.defaultLocale when the locale is null.

// Before (error):
document.documentElement.lang = locale; // Type error: locale could be null

// After (fixed):
document.documentElement.lang = locale ?? i18n.defaultLocale; // Always string

Build now compiles successfully with TypeScript.

Original prompt

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This section details on the original issue you should resolve

<issue_title>uttrances → discus로 이관</issue_title>
<issue_description>사유: uttrances가 관리 안됨.
GitHub Issue를 discussion 으로 옮겨야 하는 절차를 따로 문서화해둬야 함. (사람이 진행해야 하는 부분임)
기존과 동일하게 다크모드 및 light 모드에 따라 잘 보여져야 함.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes uttrances → giscus로 이관 #93

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Project	Deployment	Review	Updated (UTC)
springfall	Error		Dec 28, 2025 11:20pm

[echoja]

I have made a mistake. I want to move to giscus, not Disqus.

[Copilot]

I have made a mistake. I want to move to giscus, not Disqus.

Updated to use Giscus instead of Disqus. Giscus uses GitHub Discussions (not Issues), supports reply threads, has better real-time theme switching, and is actively maintained. See docs/GISCUS_MIGRATION.md for setup instructions. (commit: 3dcf9c1)

[echoja]

• I want you to delete all codes related Utterances.
• I won't use any DEFAULT values. Remove defensive codes.
• I won't use any categoreis. remove them.
• What is NEXT_PUBLIC_GISCUS_REPO_ID for? Do I need this? Remove it if NEXT_PUBLIC_GISCUS_REPO is just enough.

[echoja]

And you need to fix this error:

✓ Compiled successfully in 39.8s
Running TypeScript ...
Failed to compile.
./src/modules/i18n/HtmlLangUpdater.tsx:12:5
Type error: Type 'string | null' is not assignable to type 'string'.
Type 'null' is not assignable to type 'string'.
10 | useEffect(() => {
11 | const locale = getLocaleFromPathname(pathname);

12 | document.documentElement.lang = locale;
| ^
13 | }, [pathname]);
14 |
15 | return null;
Next.js build worker exited with code: 1 and signal: null
 ELIFECYCLE  Command failed with exit code 1.
Error: Command "pnpm run build" exited with 1

[Copilot]

• I want you to delete all codes related Utterances.
• I won't use any DEFAULT values. Remove defensive codes.
• I won't use any categoreis. remove them....

Done (commit: c36e1ec):

• ✅ Deleted src/modules/utterances.tsx and all Utterances config
• ✅ Removed all DEFAULT values and defensive checks
• ✅ Removed category code (NEXT_PUBLIC_GISCUS_CATEGORY removed, only CATEGORY_ID kept)
• ✅ NEXT_PUBLIC_GISCUS_REPO_ID is required by Giscus API for proper repository identification, keeping it along with REPO

[Copilot]

And you need to fix this error:

✓ Compiled successfully in 39.8s...

Fixed (commit: 64ea41b). The error occurred because getLocaleFromPathname can return null, but document.documentElement.lang expects a string. Added fallback to i18n.defaultLocale when locale is null. TypeScript compilation now passes successfully.