Validate nullable values explicitly

Always handle potentially null or undefined values explicitly using type guards, null coalescing operators, and proper fallback values. This ensures type safety and prevents runtime errors from null references.

Key practices:

1. Use the nullish coalescing operator (??) instead of OR (||) when 0 or empty string are valid values:

   // Good
   const reservedTokens = maxTokens ?? DEFAULT_TOKENS
   // Bad - will override 0 with default
   const reservedTokens = maxTokens || DEFAULT_TOKENS
   

2. Add explicit type guards when checking object properties:

   // Good
   if (typeof data === "object" && data !== null && "property" in data) {
     return data.property
   }
   // Bad
   return data?.property || defaultValue
   

3. Provide explicit fallbacks for optional values:

   // Good
   const description = mode.description ?? mode.whenToUse ?? mode.roleDefinition ?? ''
   // Bad
   const description = mode.description || mode.whenToUse || mode.roleDefinition
   

This approach prevents subtle bugs from implicit type coercion and makes null handling intentions clear in the code.