Implement useMemo and a Context Data Provider

Challenge summary

Implement useMemo yourself, then build a context that serves one API request to several components with loading, error and reload states. The behavior checks count computations and requests so shortcuts show up.

What you'll practice

• Explain how a memo hook decides when to recompute.
• Compare dependencies the way React does, including the edge cases of Object.is.
• Share one request between many consumers through a provider.
• Keep a context value stable so unrelated renders stay cheap.

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