Add unit test for IEnumerable handling in Engine node validation

[Copilot]

The Engine node's IsSupportedDataNodeDynamoType method was recently fixed to accept IEnumerable instead of only ArrayList, since ParseJSON returns IEnumerable<object>. This PR adds comprehensive unit test coverage for that fix.

Test Coverage

The new test IsSupportedDataNodeDynamoType_HandlesIEnumerableFromParseJSON() verifies:

• IEnumerable collections from ParseJSON are validated correctly as lists
• Strings are excluded from IEnumerable treatment (critical edge case - strings implement IEnumerable<char>)
• Various IEnumerable implementations (List<T>, parsed JSON arrays) work consistently
• Single value vs. list detection logic remains correct

// ParseJSON returns IEnumerable, not ArrayList
var parsedArray = DSCore.Data.ParseJSON("[1, 2, 3]");
var isValid = DSCore.Data.IsSupportedDataNodeDynamoType(parsedArray, typeof(int), true);
// isValid is now true (was false before the fix)

// Strings correctly excluded despite implementing IEnumerable
var str = "hello";
var isValidList = DSCore.Data.IsSupportedDataNodeDynamoType(str, typeof(string), true);
// isValidList is false (strings aren't treated as char arrays)

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[QilongTang]

@saintentropy @mjkkirschner I asked agent to add unit test for your other PR, PTAL

[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[QilongTang]

@copilot Rebase

[Copilot]

@copilot Rebase

The rebase has been completed successfully. The branch has been rebased onto the latest saintentropy-patch-1 (commit 3127149), removing the merge commit and creating a linear history. However, I'm unable to force-push due to permission constraints in the current environment. The rebased commits are:

• 62e0e839: Initial plan
• 349f9b67: Add unit test for IEnumerable handling from ParseJSON
• 13e330a4: Rename test method for consistency with tested method name

The force push will need to be completed manually or the GitHub Actions permissions may need to be adjusted to allow the push.