fix: [#1896] Call disconnectedFromNode on children in disconnectedFromNode

[TrevorBurnham]

Fixes #1896

Problem

In Node.disconnectedFromNode(), child nodes were incorrectly calling connectedToNode() instead of disconnectedFromNode().

// Before (incorrect)
const childNodes = this[PropertySymbol.nodeArray];
for (let i = 0, max = childNodes.length; i < max; i++) {
    childNodes[i][PropertySymbol.connectedToNode]();  // Wrong!
}

This bug caused nested children to not be properly disconnected when their parent was removed from the document, leaving isConnected as true for grandchildren and deeper descendants.

Solution

Changed the call from connectedToNode() to disconnectedFromNode():

// After (correct)
const childNodes = this[PropertySymbol.nodeArray];
for (let i = 0, max = childNodes.length; i < max; i++) {
    childNodes[i][PropertySymbol.disconnectedFromNode]();
}

I've added test coverage to prevent future regressions.

[TrevorBurnham]

CI is failing due to #2022, which should be fixed by #2023.