feat(bt)!: Remove legacy tree definition format

The `LegacyTreeDef` type and its normalization path have been removed.
All tree definitions must now use the factory functions (`leaf`,
`sequential`, `parallel`, `selector`, `random`, `repeat`). The
`TreeDef` type is now simply `TaskEntityDef`.

src/bt/index.ts

@@ -23,10 +23,4 @@ export {
   random,
   repeat,
 } from "./tree-def";
-export type {
-  TreeDef,
-  LegacyTreeDef,
-  TaskEntityDef,
-  LeafTaskMeta,
-  LeafFn,
-} from "./tree-def";
+export type { TreeDef, TaskEntityDef, LeafTaskMeta, LeafFn } from "./tree-def";

src/bt/tree-def.ts

@@ -22,15 +22,6 @@ export type LeafFn =
   | ((world: World, dt: number) => void)
   | (() => Generator<number | void, void, number>);
 
-/** Legacy declarative behaviour-tree definition. */
-export type LegacyTreeDef =
-  | { kind: "leaf"; run: LeafFn }
-  | { kind: "sequential"; children: LegacyTreeDef[] }
-  | { kind: "parallel"; children: LegacyTreeDef[] }
-  | { kind: "selector"; children: LegacyTreeDef[] }
-  | { kind: "random"; children: LegacyTreeDef[] }
-  | { kind: "repeat"; child: LegacyTreeDef };
-
 export interface LeafTaskMeta {
   readonly run: LeafFn;
 }
@@ -40,8 +31,8 @@ export type TaskEntityDef = EntityDef<
   LeafTaskMeta | undefined
 >;
 
-/** Behaviour-tree definitions accepted by `buildTree`. */
-export type TreeDef = LegacyTreeDef | TaskEntityDef;
+/** Behaviour-tree definition accepted by `buildTree`. */
+export type TreeDef = TaskEntityDef;
 
 // ── Entity task factories ──────────────────────────────
 
@@ -118,37 +109,14 @@ export function repeat(
 
 // ── Builder ───────────────────────────────────────────
 
-function isEntityDef(def: TreeDef | EntityDef): def is EntityDef {
-  return def.kind === "entity";
-}
-
-function normalizeLegacyTree(def: LegacyTreeDef): TaskEntityDef {
-  switch (def.kind) {
-    case "leaf":
-      return leaf(def.run);
-    case "repeat":
-      return repeat(normalizeLegacyTree(def.child));
-    case "sequential":
-      return sequential(def.children.map(normalizeLegacyTree));
-    case "parallel":
-      return parallel(def.children.map(normalizeLegacyTree));
-    case "selector":
-      return selector(def.children.map(normalizeLegacyTree));
-    case "random":
-      return random(def.children.map(normalizeLegacyTree));
-  }
-}
-
 /**
  * Materialize a behaviour-tree definition into ECS entities and return a
  * fully-wired `TaskRunner`.
  *
- * The preferred definition format is an `EntityDef` tree produced by the task
- * factories (`leaf`, `sequential`, `parallel`, `selector`, `random`, `repeat`)
- * and generic single-component entity factories. Non-task child entities are
- * materialized into the ECS tree but ignored by `TaskRunner` execution.
- *
- * Legacy object definitions are still accepted for compatibility.
+ * Definitions are `EntityDef` trees produced by the task factories (`leaf`,
+ * `sequential`, `parallel`, `selector`, `random`, `repeat`) and generic
+ * single-component entity factories. Non-task child entities are materialized
+ * into the ECS tree but ignored by `TaskRunner` execution.
  *
  * Leaf `run` functions:
  * - **Plain function** — runs once per tick. `return` = success. `throw` = fail.
@@ -158,7 +126,6 @@ function normalizeLegacyTree(def: LegacyTreeDef): TaskEntityDef {
  *   Generator completion = success. `throw` = fail. `throw Cancel` = cancel.
  */
 export function buildTree(world: World, def: TreeDef): TaskRunner {
-  const rootDef = isEntityDef(def) ? def : normalizeLegacyTree(def);
   const leafHandlers = new Map<Entity, LeafFn>();
   // Track generator iterators for multi-frame leaves
   const generators = new Map<Entity, Generator<number | void, void, number>>();
@@ -189,7 +156,7 @@ export function buildTree(world: World, def: TreeDef): TaskRunner {
     return entity;
   }
 
-  const root = build(rootDef);
+  const root = build(def);
 
   if (!world.has(root, Task)) {
     throw new Error("buildTree root must be a task entity");