feat(bt): Rename repeat to cycle and refactor runner

Rework task execution to be synchronous within a single tick.
Scheduling boundaries are now defined by `cycle` nodes, which
replace the previous `repeat` decorator.  All tasks are executed
immediately when scheduled, and parent/child propagation is
handled inline.

examples/tetris/main.ts

@@ -4,7 +4,7 @@
 //   Behaviour Tree (buildTree) — controls game flow:
 //     parallel
 //       ├── gravityTick (leaf)    — generator loop, auto-drop piece on timer
-//       └── repeat
+//       └── cycle
 //             └── seq (sequential)
 //                   ├── handleInput (leaf)  — reads queued commands
 //                   └── render (leaf)       — draws via blessed
@@ -24,7 +24,7 @@ import {
   buildTree,
   leaf,
   parallel,
-  repeat,
+  cycle,
   sequential,
 } from "../../src/bt/index";
 import { CommandQueue } from "../../src/commands/index";
@@ -95,7 +95,7 @@ const runner = buildTree(
         }
       }
     }),
-    repeat(
+    cycle(
       sequential([
         leaf(() => {
           commands.execute();