Add some UI

.claude/docs/systems.md

@@ -9,6 +9,8 @@
 
 ## Entities (Overworld)
 
+See [Overworld](overworld.md) for the full reference (scene structure, interaction types, camera, map transitions).
+
 - All interactable world objects extend `Entity` (CharacterBody3D)
 - Interaction type set via `@export var interactType:InteractType`
 - Interaction routing lives in `EntityInteractableArea.onInteract()` — add new `InteractType` values there
@@ -21,6 +23,8 @@
 
 ## UI
 
+See [UI](ui.md) for the full reference (VNTextbox, ClosableMenu, pause/debug/settings menus, AdvancedRichText, adding new menus).
+
 - `UI.TEXTBOX.setTextAndWait(text)` — show dialogue and await player dismiss (use `await`)
 - Movement is blocked automatically when `UI.TEXTBOX` is visible (`EntityMovement._canMove()` checks this)
 - Menus extend `ClosableMenu` for open/close/toggle + `closed`/`opened` signals