getAllNodes Should Return Subclass Nodes

1. Create metamodel with A and B, B inherits from A
2. Create a model with A's and B's
3. Write a rule and have getAllNodes('A') in the LHS condition
4. Observe that the B nodes are not returned.

Reason: In mmmk.js, lines 692-705, the '$type' of the node is directly matched against.

Proposal: getAllNodes should be extended with an extra boolean parameter 'includeSubclasses' which then instructs the function to include the sub class nodes.

Start in mmmk.js around lines 692-705 and reproduce the reported metamodel/model setup with A and subclass B. Trace how getAllNodes('A') matches node types, then verify that the optional includeSubclasses behavior returns both A and B nodes while preserving the existing behavior when it is not enabled.

Written by the indexing model from the issue text.