Add object identity fields with on-canvas info display

[SilicoBen]

Summary

• Objects placed in Object mode get four identity fields — GlobalID, TypeID, CustomID, Name.
  • GlobalID runs 0,1,2… across the apparatus; TypeID runs 0,1,2… within each object type.
  • CustomID defaults to {GlobalID}_{TypeID}; Name defaults to {TypeName}_{GlobalID}_{TypeID}.
  • All four are editable from the object inspector; uniqueness is not enforced.
• Default counters derive from the highest existing numeric value, so they survive save/load and undo without extra state. Pre-existing project files get sequential defaults backfilled on load.
• A Show item info toggle in the Object-types panel draws each object's four fields beside its icon. Lines render green normally, red when the value overlaps another object — TypeID overlap is scoped per type, the rest globally.

Dependency

Requires OpenApparatus/core#5 (adds the fields to RoomObject and the serialization layer). Merge that first.

Test plan

• Place several objects of mixed types; confirm GlobalID/TypeID sequences.
• Edit each field in the inspector; confirm edits persist and repaint.
• Toggle "Show item info"; confirm labels appear and overlap detection colours correctly.
• Save/reload and undo/redo; confirm identity fields are stable.
• Load a project saved before this change; confirm defaults backfill.