Say that keys ignore case in behaviors (#227)

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

Behaviors.md

@@ -101,6 +101,9 @@ shown on the node and editable in the inspector.
   sideways slide of a Tetris piece, or a held arrow walking a menu. The browser's own key repeat is
   deliberately not used: its delay and rate are an operating-system setting, not a game's. Both
   rows stay off the node body while the delay is 0, so a plain key node keeps its single line.
+- **Keys ignore case**: a letter is the same key with or without Shift or Caps Lock, so a key node
+  set to `a` also hears `A`, and a key picked with Shift held is stored lower-case. A key is let go
+  under the name it went down as, even when Shift changes in between (`1` down, `!` up).
 - **Node set** (`src/core/graph/nodes/`, one file per node): events `On start`, `On enable`, `On update`, `On disable`, `On destroy` (see *Lifecycle*), `On key down/up/held`,
   `On timer` (fires on the first frame past each due time; `late` says by how much, so `time - late` is exactly a multiple of the interval), `On collision enter/stay/exit` (stay every frame, or with an interval; while playing enter and stay tell normal, impulse and point of the contact), `On click` (the mouse pressed on the owner — anywhere when it has none), `On animation finished`, `On state entered`, `On state exited` (one output per state, see *State machines*), `Start` · flow `Branch`, `Sequence`, `Repeat`, `Run behavior`, `End`, and the four that move or follow a state machine, `State branch`, `Set state`, `Set state by name`, `State transition` (see *State machines*) · data `Self`, `Owner`, `Parent`, `Object by name`, `Name of`,
   `Is asset` (is this object an instance of asset X — how you tell what you collided with),