[Builder] Validate Attempted Pin Connections before Making Them

When the user tries to connect two pins together, validate whether they are of a compatible type before making the connection.

If they are not, clearly inform the user, and do not make the connection.

If they are, proceed as usual.

Start by locating the Builder code that handles attempted pin connections and the existing pin type definitions or validation flow. Trace what happens when two pins are connected, then verify that incompatible types produce a clear user message and no connection, while compatible types retain the current behavior.

Written by the indexing model from the issue text.