A shared value belongs to the run, so a declaration carries its scope (#91)

A variable or a state machine declared `global` keeps one value for the whole
run instead of one per behavior instance. The scope sits on the declaration --
`PropertyDef.scope` and `StateMachineAsset.scope`, both optional, absence
meaning `local` -- and `local` is never written, so every project made before
this saves back unchanged.

**The name is the key.** Two behaviors declaring a global `score` mean one
variable; a behavior declaring `score` locally keeps its own. Kinds that
disagree about one global name stop the run before it starts, with the two
behaviors named; starting values that disagree are a warning on the behavior
that declares it, and the first declaration wins (`globalConflicts`).

The runtime needs no redirection layer. A global variable falls out of
`schemaForObject`, so it never reaches `entity.props` -- and then the whole rule
is "whoever declares the name takes their own value" (`graph/sharedState.ts`).
The `Variables` node is untouched and stays transparent: switching a variable to
global breaks no existing graph, because `GraphInterpreter.readAll` builds a
fresh object per read anyway and only asks `port.key in all`.

That same cut answers the inspector. A shared value has no owner, so the placed
object shows no row for it and can hold no override -- `SetVariableScopeCommand`
takes the deviations that were there and undo gives them back.

Both places say it in words rather than leaving a glyph to be guessed: the
declaration explains the mark below the list, and the placed object names the
variable it no longer holds instead of claiming the behavior declares none --
which is what it said before, untruthfully. Screenshots of the e2e run turned
that up; no check had been looking at it.

`SharedState` hangs off `NodeContext`, is built in `BehaviorSystem.start()` from
the *declarations* rather than from any instance (a global variable exists
before its behavior is placed), and is thrown away with the run: nothing is
written back, not even in the editor run. `GraphInterpreter.call` passes it on
through `...ctx` while nested calls keep getting fresh local variables, which is
why `program.defaults` is stripped of global keys.

Two traps this hit. `defSignature`/`assetSignature` have to carry the scope or
the inspector does not rebuild after the switch -- and a state machine has no
rows at all, so its scope is appended to the signature by hand. And the object
inspector does not go through `schemaForObject` for behaviors, it reads
`asset.variables` directly; filtering in one place was not enough, and no unit
test covered that path. The e2e caught it (`global: true` where false belonged),
and the rule now lives in one named function, `objectRows`.

Scopes `object` and `scene` are deliberately not built. The object case already
has a route (`Object by name` -> `Properties`), and a run knows exactly one
scene, so `scene` would be indistinguishable from `global` until #39 exists.

Closes #59: a machine's scope is a word on the machine asset, not a setting per
`Set state` node, so the same machine cannot live in two places at once.

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

src/core/graph/nodes/flow/StateTransition.ts

@@ -1,6 +1,7 @@
 import { textOf } from '../../../model/Properties';
 import { flatDef } from '../../../properties/PropertySchema';
 import type { NodeDef } from '../../NodeRegistry';
+import { stateBag } from '../../sharedState';
 import { machinePort, STATE_TRANSITION, TRANSITION_PARAM, transitionTo } from '../../stateMachine';
 import { asString } from '../../values';
 import { exec } from '../shared';
@@ -18,11 +19,12 @@ export const StateTransition: NodeDef = {
   params: [flatDef(TRANSITION_PARAM, 'text', { label: 'Transition', value: '' })],
   run: (ctx, inputs, params, _def, _entry, lookup) => {
     const id = asString(inputs.machine);
-    const current = ctx.states[id] ?? '';
+    const states = stateBag(ctx, id);
+    const current = states[id] ?? '';
     const machine = current ? lookup.machine(id) : null;
     const name = textOf(params[TRANSITION_PARAM] ?? '');
     const target = machine ? transitionTo(machine, current, name) : '';
-    if (target) ctx.states[id] = target;
+    if (target) states[id] = target;
     return { next: 'exec' };
   },
 };