Let On key down repeat while the key stays held

A held key fired once and then nothing, so sliding a Tetris piece sideways or
walking a menu meant building a timer next to every key node. Two settings on
the node do it now: Repeat after and Repeat interval, both in milliseconds so
the usual values stay whole numbers (300, 50) instead of 0.3 and 0.05. A delay
of 0 keeps the node exactly as it was, an interval of 0 means every frame.

The browser's own auto-repeat is deliberately not used - Input.press has always
dropped it - because its delay and rate are an operating-system setting of the
player's, not a game's. The repeat is built from the measured hold time instead,
per node, so two nodes on one key keep their own clocks. The rule itself is a
pure function in keyRepeat.ts and is checked without a world.

Both rows stay off the node body while the delay is 0: two lines of "0" on every
key node in every graph would be noise, and the screenshot said so. NodeDef gains
hiddenParams for that; the inspector still shows them.

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

src/core/graph/NodeRegistry.ts

@@ -51,6 +51,11 @@ export interface NodeDef {
   outputs: PortDef[];
   /** Node settings that are not ports (key name, operator, variable). */
   params: PropertyDef[];
+  /**
+   * Settings that say nothing at this value set, so the node body leaves them off; the inspector
+   * still offers them. Without it a switched-off repeat is two rows of "0" on every key node.
+   */
+  hiddenParams?(params: PropertyBag): string[];
   /**
    * Pure data nodes are evaluated on demand when a downstream input needs their value; exec nodes
    * run when the flow reaches them. Event nodes have no `run` – the interpreter seeds their outputs.