[ladder-editor] P0: Default template has no logic — blank canvas on first open

[Mikecranesync]

The default program loaded on startup is:

PROGRAM Untitled
VAR
  // Declare variables here
END_VAR
  // Write your ladder logic here
END_PROGRAM

This contains zero logic statements, so the ladder canvas is completely blank. New users see a black canvas and have no idea the tool works.

Fix: Replace default template with a working example (e.g. the MIRA Phase 1 conveyor program or a simple traffic light). The ladder should render immediately on first open.

Evidence: Test 04 — Default program nodes: 0