fix: 终端延迟到容器有尺寸后再 open（零尺寸初始化崩溃，WKWebView 底部面板展开后终端空白，#25）

src/client/open-when-sized.ts

@@ -0,0 +1,43 @@
+/**
+ * Deferred one-shot open for hosts that may not have a real size yet.
+ *
+ * xterm's `Terminal.open()` must not run in a zero-size container: the
+ * renderer creation fails there (the DomRenderer is built from the host's
+ * dimensions), leaving the render service's renderer `undefined`, and the
+ * next Viewport refresh crashes reading `.dimensions` off it. WebKit-based
+ * hosts (WKWebView) reliably report zero while the bottom panel's expand
+ * slide is in flight; any `display:none`-hidden ancestor does the same.
+ *
+ * The caller's `open` callback (open + fit + resize) is invoked exactly
+ * once, on the first frame where the host reports a real size. While the
+ * host stays zero-sized the polling continues every frame; it stops when
+ * the host leaves the document (`isConnected`), so a pending open never
+ * fires after unmount. The returned cancel function drops a pending frame
+ * immediately (idempotent).
+ *
+ * `raf`/`caf` are injectable so tests can drive the polling deterministically.
+ */
+export function openWhenSized(
+  host: HTMLElement,
+  open: () => void,
+  raf: (cb: FrameRequestCallback) => number = requestAnimationFrame,
+  caf: (id: number) => void = cancelAnimationFrame,
+): () => void {
+  let frame: number | null = null
+  const step = (): void => {
+    frame = null
+    if (!host.isConnected) return
+    if (host.clientWidth > 0 && host.clientHeight > 0) {
+      open()
+      return
+    }
+    frame = raf(step)
+  }
+  frame = raf(step)
+  return () => {
+    if (frame !== null) {
+      caf(frame)
+      frame = null
+    }
+  }
+}