修：draw-ui / oil-motion 原被当子模块指针收录 ⇒ 改为正常文件入库（两份内容原先对别人是空的）

一、问题（本轮实测）
`draw-ui` 与 `oil-motion` 目录里**各自带一个内嵌 `.git`** ⇒ 上一次提交把它们记成了 **gitlink（子模块指针）**
⇒ 仓库里只存了一个不属于任何远端的 commit id，**别人克隆下来这两份是空的** ✗（`git status` 显示 ` m draw-ui` / ` m oil-motion` ＝ 子模块内容有改动）。

二、处置（可回退）
· 把两处的 `.git` **挪走**（⛔ 不是删除）⇒ `归档/内嵌git-20261008/{draw-ui,oil-motion}.git`；
· `git rm --cached` 掉那两个 gitlink，再 `git add` 两个目录 ⇒ **按正常文件入库**（内容才真的进仓库）。

三、副作用（如实记）
挪走 `.git` 后，这两个技能**不能再原地 `git pull` 取上游更新**（要更新得重新拉一份覆盖）；
如需恢复其本地仓库，把 `归档/内嵌git-20261008/` 里的 `.git` 挪回原处即可。

oil-motion/assets/step-gesture.ts

@@ -0,0 +1,78 @@
+export type StepDirection = -1 | 1;
+
+export type StepGestureOptions = {
+  threshold?: number;
+  idleMilliseconds?: number;
+  onStep: (direction: StepDirection) => void;
+};
+
+export type StepGestureAdapter = {
+  feed(delta: number): void;
+  setProgrammaticNavigation(active: boolean): void;
+  reset(): void;
+  destroy(): void;
+};
+
+export function createStepGestureAdapter(
+  options: StepGestureOptions,
+): StepGestureAdapter {
+  const threshold = Math.max(1, options.threshold ?? 40);
+  const idleMilliseconds = Math.max(16, options.idleMilliseconds ?? 140);
+  let accumulated = 0;
+  let lockedDirection: StepDirection | 0 = 0;
+  let programmaticNavigation = false;
+  let releaseTimer = 0;
+  let destroyed = false;
+
+  const clearRelease = () => {
+    if (releaseTimer) window.clearTimeout(releaseTimer);
+    releaseTimer = 0;
+  };
+
+  const reset = () => {
+    clearRelease();
+    accumulated = 0;
+    lockedDirection = 0;
+  };
+
+  const scheduleRelease = () => {
+    clearRelease();
+    releaseTimer = window.setTimeout(reset, idleMilliseconds);
+  };
+
+  return {
+    feed(delta: number) {
+      if (
+        destroyed ||
+        programmaticNavigation ||
+        !Number.isFinite(delta) ||
+        delta === 0
+      ) return;
+      const direction: StepDirection = delta < 0 ? -1 : 1;
+      if (lockedDirection === direction) {
+        scheduleRelease();
+        return;
+      }
+      if (lockedDirection === -direction) {
+        accumulated = 0;
+        lockedDirection = 0;
+      }
+      if (accumulated && Math.sign(accumulated) !== direction) accumulated = 0;
+      accumulated += delta;
+      scheduleRelease();
+      if (Math.abs(accumulated) < threshold) return;
+      accumulated = 0;
+      lockedDirection = direction;
+      options.onStep(direction);
+    },
+    setProgrammaticNavigation(active: boolean) {
+      programmaticNavigation = active;
+      if (active) reset();
+    },
+    reset,
+    destroy() {
+      destroyed = true;
+      reset();
+    },
+  };
+}