Tell a graph the frame a key went down or came up

Key is down says whether a key is held. To act once on a press, a
graph had only the events On key down and On key up. A behavior
that is called by another one and reads its input as data had to
keep the state of the last frame in a variable of its own.

- Key was pressed is true for the one frame in which the key goes
  down, the frame On key down fires in. Key was released is the
  same for the frame the key comes up.
- Both sit next to Key is down in the palette and have the key as
  their only setting.
- NodeContext gains wasKeyPressed and wasKeyReleased. The behavior
  context answers them from justPressed and justReleased of the
  input, through keyName, so a key saved as "A" meets the key "a".
- No repeat. On key down may fire again while a key stays held, a
  held key is pressed once here.
- When the window loses the keyboard, every held key counts as
  released in that frame, as On key up has it.
- The engine prompt of the benchmark names the two nodes.

Tests:
- Gate on melektaus-atx right before this commit: 213 files, 3278
  tests (3264 + 14), exit 0.
- e2e 18,20,43 on melektaus-atx: 57 checks, all pass.
- Ten unit tests in key-edges.test.ts on a real world, four cases
  in the node catalog.
- Eight counter-probes all fail their tests. One did not at first
  (the case of the key saved on the node), a test was added.
- No e2e check of its own, the sum stays 1676. The nodes were not
  looked at in the browser, neither in the palette nor with a real
  keyboard.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

benchmark/engine-prompt.md

@@ -211,7 +211,7 @@ Implement all of these. Names are the palette names.
 - **Math and logic:** `Add`, `Subtract`, `Multiply`, `Divide` (by 0 gives 0), `Modulo`, `Min`, `Max`, `Abs`, `Sqrt`, `Clamp`, `Floor`, `Ceil`, `Round`, `Lerp` (with ease: Linear, In, Out, In-out, or a curve asset), `Random`, `Length`, `Distance`, `Normalize`, `Compare`, `Equals`, `And`, `Or`, `Not`, `Select`, `First not empty`, `Time`. `Compare` and `Equals` treat two numbers as equal up to a relative 1e-9.
 - **Text:** `To text`, `To number`, `Join text`, `Substring`, `Find text`.
 - **Lists and structs:** `List` (constant), `Fill`, `Count`, `Item at`, `Set item`, `Add item`, `Sub list`, `Join lists`, `Index of`, `Pack`, `Expand`. List nodes return new lists and leave their input alone.
-- **Input:** `Key is down`, `Axis input` (four keys to a normalised direction), `Mouse position`, `Mouse button`, `Is hovered`.
+- **Input:** `Key is down`, `Key was pressed` and `Key was released` (true for the one frame of the edge), `Axis input` (four keys to a normalised direction), `Mouse position`, `Mouse button`, `Is hovered`.
 - **Actions:** `Move` (dx, dy, scale, dt; optional *Collide with solids*, section 11), `Set position`, `Spawn` (asset, x, y, z, optional parent; outputs the object), `Destroy`, `Emit`, `Play sound`, `Stop sound`, `Play animation`, `Stop animation`, `Pause animation`, `Load scene`, `Log`, `Stop game`, `Restart game`, `Pause game`, `Resume game`, `Set time scale`.
 - **Queries:** `Is touching`, `Raycast`, `Raycast all`, `Get velocity`, `Animation playing`, `Animation length`, `Current state`, `Is in state`, `Is game paused`, `Time scale`.
 - **Physics:** `Apply force`, `Apply impulse`, `Set velocity`, `Set angular velocity`, `Set gravity`, `Ignore one-way`.