test: add third-party script error handling and duplicate prevention coverage

[JemimahEkong]

PR: test(third-party): add script error handling and duplicate prevention coverage

This PR improves third-party script reliability by adding coverage for script load failures and preventing duplicate script injection scenarios.

Problem

The third-party script loading module lacked tests for two important edge cases:

1. Handling failed third-party script loads through error events.
2. Preventing duplicate script entries from creating multiple DOM script nodes.

What changed

src/lib/thirdParty.ts

• Added optional onError?: () => void support to ThirdPartyScript so consumers can provide script-specific failure handlers.

• Added duplicate script protection in getThirdPartyScripts():

  • Scripts with duplicate id values are filtered out.
  • Prevents accidental duplicate script injection at the configuration layer.

• Exported handleScriptError(script) helper:

  • Safely invokes a configured error callback when a script fails to load.

src/components/ThirdPartyScripts.tsx

• Updated script rendering logic to:

  • Extract onError from each script configuration.
  • Forward it to the Next.js <Script onError={...}> handler.

Test coverage

Added 2 new tests in:

src/__tests__/lib/thirdParty.test.ts

Covered scenarios:

✅ Script load error handling

• Confirms default scripts do not define error handlers.
• Verifies custom onError callbacks are executed through handleScriptError.

✅ Duplicate script prevention

• Confirms returned scripts always contain unique IDs.
• Ensures duplicate configurations cannot result in duplicate script injection.

Validation

• ✅ All 12 tests passing

  • 10 existing tests
  • 2 new tests

• ✅ No regressions introduced

Closes #844

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[sshdopey]

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