3.2.0-pre — Graph Link Editing, Legacy Format & Edge Visibility

✨ New Features

Add/Remove Links (Two-Step Workflow): Navigation edges between graph nodes can now be added and removed interactively. Select node A, press Alt++ to mark it as the link source (green double-ring indicator), select node B, press Alt++ again to create the link. Use Alt+- to remove a link the same way.
Node Label Toggle: On-screen node ID labels can now be toggled on/off with Alt+L. The title banner shows [labels off] when disabled.
Legacy Graph Format Support: Added a parser, full writer, and position-patch saver for the undocumented alternate tagged graph format (1-byte type tags: 0x05=int32, 0x06=float, 0x08=Vec3d, 0x09=string, no magic number). This fixes the "bad magic" error that prevented level 8's graph1.dat and graph7.dat (and other legacy graphs) from loading and displaying.

Fixed: "Bad magic" error on level 8 graph1: Graph files using the legacy tagged format (no 0xFFEEDDCC magic) are now auto-detected and parsed transparently — both standard and legacy formats produce the same editable GraphFile and support full add/remove/edit/save.
Fixed: Links not visible / not above ground: Edge lines were drawn at node Z (ground level), getting buried under terrain. Edges now render at the vertical centre of the node boxes (z + H) so they sit above ground and are clearly visible.

Event	Binding	Action
`AddGraphLink`	`<Alt><Plus>`	Two-step: mark source node, then link to target node
`RemoveGraphLink`	`<Alt><Minus>`	Two-step: mark source node, then unlink target node
`ToggleGraphNodeLabels`	`<Alt><L>`	Toggle on-screen node ID labels

Added 4 new tests for the legacy graph format: parse validity, node data sanity, write round-trip, and position-patch save.
31/32 graph tests pass (1 pre-existing failure in WriteUnchangedIsByteIdentical, unrelated to this release).