feat(hooks): add todo-description-override hook to enforce atomic todo format

Override TodoWrite description via tool.definition hook to require
WHERE/WHY/HOW/RESULT in each todo title and enforce 1-3 tool call
granularity.

src/hooks/todo-description-override/hook.ts

@@ -0,0 +1,14 @@
+import { TODOWRITE_DESCRIPTION } from "./description"
+
+export function createTodoDescriptionOverrideHook() {
+  return {
+    "tool.definition": async (
+      input: { toolID: string },
+      output: { description: string; parameters: unknown },
+    ) => {
+      if (input.toolID === "todowrite") {
+        output.description = TODOWRITE_DESCRIPTION
+      }
+    },
+  }
+}