Replace the property nodes with one Properties node

Get/Set property, Get/Set properties, Set enabled and Set text are gone.
A single Properties node takes a fixed "object" input; every chosen
property is an output that reads the current value, and one switched to
Set is also an input written when the flow arrives. Exec pins only exist
while at least one entry writes.

The node carries a type (Sprite, Text, Collider, Camera, Container,
Behavior, Any) that decides what "+ Property" offers: the fields of that
type, the variables of the chosen behavior, or for Any a kind to pick
and a name to type. Each port takes the default and field of its type,
so a Camera width starts at 640. Switching the type keeps the ports and
marks those the new type lacks. At runtime the type is only an editor
aid; the node writes to whatever object it gets.

Old project files are converted on load. The type is inferred from the
keys: the first object type that has them all, else the one behavior
that declares them all, else Any. enabled belongs to every object, so a
converted Set enabled lands on Any.

The jump-run and tetris seeders use Properties throughout; draw-piece
switches its cell on in the same node that sets the colour.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/core/enabled.test.ts

@@ -111,7 +111,7 @@ describe('the enabled switch', () => {
     world.tick(0.1);
     expect(entity.props.ticks).toBe(0); // off: no On start, no ticks
 
-    entity.props.enabled = true; // what "Set enabled" does
+    entity.props.enabled = true; // what Properties with `enabled` set does
     world.tick(0.1);
     expect(entity.props.ticks).toBe(2); // On start plus this frame's On update
     world.tick(0.1);