A state change is something the graph can react to, so the machine announces it (#53, #54, #55, #57)

Four issues that all reach for the same line: how the current state is
read and written. Splitting them into four commits would mean four
states of the tree that do not compile, so they arrive together.

#55 start state — the machine asset carries an optional `start` holding
a State node's id. Right-click a state to set or remove it, a ring in
the node's title says which one it is. A dead id (the state was deleted)
reads as "no start", so nothing has to clean up after a deletion.

#53 entered/exited — `On state entered` and `On state exited`, one exec
output per state. Every change now goes through a single `setState`
that reports it; BehaviorSystem delivers it after the exec flow that
caused it, `exited` of the old before `entered` of the new, round after
round until the queue is empty, with a cap that stops a ping-pong graph
with an endless-loop error. A local machine tells the instance that
switched, a global one tells every instance holding a matching event
node. The start state fires `entered` too: per instance for a local
machine, once per run for a global one.

#57 reading — `Current state` with `name` for showing and `id` for
comparing, `Is in state` with one boolean per state. Neither has a
`run`, so `read` learned `def` and `lookup`, and the catalog test knows
this third kind of node.

#54 seeing it — during a run the state machine tab marks every state
some instance is holding faintly, and the one held by the selected
scene object's instance strongly.

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

src/core/graph/nodes/index.ts

@@ -23,6 +23,7 @@ import { GetPosition } from './data/GetPosition';
 import { IsAsset } from './data/IsAsset';
 import { IsEnabled } from './data/IsEnabled';
 import { IsHovered } from './data/IsHovered';
+import { IsInState } from './data/IsInState';
 import { IsTouching } from './data/IsTouching';
 import { Join } from './data/Join';
 import { KeyIsDown } from './data/KeyIsDown';
@@ -61,6 +62,7 @@ import { ToNumber } from './data/ToNumber';
 import { ToText } from './data/ToText';
 import { Concat } from './data/Concat';
 import { Count } from './data/Count';
+import { CurrentState } from './data/CurrentState';
 import { ExpandStruct } from './data/ExpandStruct';
 import { Fill } from './data/Fill';
 import { IndexOf } from './data/IndexOf';
@@ -79,6 +81,8 @@ import { OnKeyDown } from './events/OnKeyDown';
 import { OnKeyHeld } from './events/OnKeyHeld';
 import { OnKeyUp } from './events/OnKeyUp';
 import { OnStart } from './events/OnStart';
+import { OnStateEntered } from './events/OnStateEntered';
+import { OnStateExited } from './events/OnStateExited';
 import { OnTimer } from './events/OnTimer';
 import { OnUpdate } from './events/OnUpdate';
 import { BehaviorEnd } from './flow/BehaviorEnd';
@@ -114,6 +118,8 @@ export const BUILT_IN_NODES: readonly NodeDef[] = [
   OnCollisionExit,
   OnClick,
   OnAnimationFinished,
+  OnStateEntered,
+  OnStateExited,
   BehaviorStart,
   Branch,
   Sequence,
@@ -122,6 +128,8 @@ export const BUILT_IN_NODES: readonly NodeDef[] = [
   StateBranch,
   SetState,
   StateTransition,
+  CurrentState,
+  IsInState,
   BehaviorEnd,
   Variables,
   Self,