feat: add unevaluatedItems lesson for closing tuples (#61)

[Avanish-Gupta-CSE]

What kind of change does this PR introduce?

Feature - Adds a new lesson for the unevaluatedItems keyword.

Issue Number:

• Closes The unevaluatedItems lesson needs work #61

Screenshots/videos:

N/A - This is a new lesson file (MDX content + code.ts with test cases).

If relevant, did you update the documentation?

N/A - This PR adds lesson content, not documentation.

Summary

Adds a new lesson demonstrating the proper use case for unevaluatedItems - closing a tuple defined in a referenced schema.

This addresses the issue where the original lesson could be solved with items instead of unevaluatedItems. The new lesson:

• Uses $ref to reference a base tuple (coordinate pair with lat/long)
• Demonstrates closing the tuple with unevaluatedItems: false
• Explains why items cannot achieve this when using schema composition

This matches the approach approved by @jdesrosiers in the issue discussion.

Lesson Files Added:

• content/07-Miscellaneous/02-Extending-Closed-Tuples-with-unevaluatedItems/instructions.mdx
• content/07-Miscellaneous/02-Extending-Closed-Tuples-with-unevaluatedItems/code.ts

Test Cases: 9 comprehensive test cases covering valid coordinate tuples and invalid scenarios (extra items, wrong types).

Does this PR introduce a breaking change?

No.

[jdesrosiers]

I can confirm that this is a correct and real world use case of JSON Schema. There's just one thing that I think can be worded better (details inline).

[jdesrosiers]

"any part of the schema" isn't quite right. Or, at least, it's a little misleading. I don't know the best way to explain it, but this example should illustrate what I mean.

{
  "allOf": [
    { "$ref": "#/$defs/coordinate" },
    { "unevaluatedItems": false }
  ],

  "$defs": {
    "coordinate": {
      "type": "array",
      "prefixItems": [
        { "type": "number" },
        { "type": "number" }
      ]
    }
  }
}

unevaluatedItems doesn't "see" the prefixItems in this case. It only "sees" the prefixItems "below" it in the schema. (Although because $ref allows you to jump around the schema it isn't always clear what "below" means). Hope that helps.

[Avanish-Gupta-CSE]

Thanks for the review !
I updated the wording to clarify that unevaluatedItems only uses annotations from the same evaluation path (subschemas "below" it) and noted the allOf-branch case. Pushed in c3755b4.

[jdesrosiers]

That looks better. Thanks for updating. I'll leave the other aspects of the review to the actual maintainers of this project.