Add visualization for invalid connections in the Graph Editor (AcademySoftwareFoundation#2921)

Detect input/output type mismatches when building the link graph and
surface them visually in three ways:

- Erroneous links are drawn in red with a heavier stroke.
- Nodes that receive a mismatched connection get a red border highlight.
- A diagnostic panel appears below the node editor, listing each mismatch
  (node name, input name, expected type, actual type); clicking an entry
  navigates to the offending node.

The `Link` struct gains an `_erroneous` flag and a new `LinkDiagnostic`
struct is introduced to carry per-mismatch metadata collected in
`linkGraph()` and consumed by `connectLinks()`, `createNodes()`, and
`drawGraph()`.

Closes AcademySoftwareFoundation#2920

Author: pixelsandpointers