桌面 GUI 外链修复 + 主题顺序调整（含结构扁平化进行中的工作区基线）

- 集成 tauri-plugin-opener：Cargo/lib.rs/capabilities/npm 四处接线，新增 src/openExternal.ts（桌面走 opener，浏览器回退 window.open，相对路径绝对化）
- 关于页 4 个链接、活动栏官网菜单、代理错误横幅 2 处健康检查链接全部改走 openExternal，桌面端可正常跳转
- 设置→外观 主题顺序调整为 深色/浅色/跟随系统
- release 二进制重编并验证（浏览器实测关于页链接可开文档页）
- 附带工作区中未提交的扁平化重构现状（另一会话进行中）
- homepage 落地页与文档终检通过（8787 / 与 /docs 双 200）

src/components/SplitPane.tsx

@@ -0,0 +1,124 @@
+import { useCallback, useEffect, useRef, useState, type ReactNode } from "react";
+
+type Props = {
+  direction?: "horizontal" | "vertical";
+  initialRatio?: number;
+  storageKey?: string;
+  minPx?: number;
+  minSecondPx?: number;
+  className?: string;
+  children: [ReactNode, ReactNode];
+};
+
+function clamp(n: number, lo: number, hi: number) {
+  return Math.min(hi, Math.max(lo, n));
+}
+
+export function SplitPane({
+  direction = "vertical",
+  initialRatio = 0.45,
+  storageKey,
+  minPx = 120,
+  minSecondPx = minPx,
+  className = "",
+  children,
+}: Props) {
+  const [a, b] = children;
+  const rootRef = useRef<HTMLDivElement | null>(null);
+  const [size, setSize] = useState(0);
+  const [ratio, setRatio] = useState(() => {
+    if (storageKey) {
+      const raw = localStorage.getItem(storageKey);
+      const n = raw ? Number(raw) : NaN;
+      if (Number.isFinite(n) && n > 0.1 && n < 0.9) return n;
+    }
+    return initialRatio;
+  });
+  const dragging = useRef(false);
+
+  useEffect(() => {
+    const root = rootRef.current;
+    if (!root) return;
+    const measure = () => setSize(direction === "vertical" ? root.clientHeight : root.clientWidth);
+    const observer = new ResizeObserver(measure);
+    observer.observe(root);
+    measure();
+    return () => observer.disconnect();
+  }, [direction]);
+
+  useEffect(() => {
+    if (storageKey) localStorage.setItem(storageKey, String(ratio));
+  }, [ratio, storageKey]);
+
+  const onPointerMove = useCallback(
+    (e: PointerEvent) => {
+      if (!dragging.current || !rootRef.current) return;
+      const rect = rootRef.current.getBoundingClientRect();
+      if (direction === "vertical") {
+        const y = e.clientY - rect.top;
+        if (rect.height) setRatio(clamp(y / rect.height, minPx / rect.height, 1 - (minSecondPx + 8) / rect.height));
+      } else {
+        const x = e.clientX - rect.left;
+        if (rect.width) setRatio(clamp(x / rect.width, minPx / rect.width, 1 - (minSecondPx + 8) / rect.width));
+      }
+    },
+    [direction, minPx, minSecondPx],
+  );
+
+  const stop = useCallback(() => {
+    dragging.current = false;
+    document.body.style.cursor = "";
+    document.body.style.userSelect = "";
+  }, []);
+
+  useEffect(() => {
+    window.addEventListener("pointermove", onPointerMove);
+    window.addEventListener("pointerup", stop);
+    return () => {
+      window.removeEventListener("pointermove", onPointerMove);
+      window.removeEventListener("pointerup", stop);
+    };
+  }, [onPointerMove, stop]);
+
+  const vert = direction === "vertical";
+  // A stored ratio can become unusable after shrinking the window. Reserve room
+  // for both panes and the separator at the current measured size.
+  const firstSize = size ? Math.min(Math.max(size * ratio, Math.min(minPx, size / 2)), Math.max(0, size - minSecondPx - 8)) : undefined;
+  return (
+    <div
+      ref={rootRef}
+      className={`flex min-h-0 min-w-0 flex-1 ${vert ? "flex-col" : "flex-row"} ${className}`}
+    >
+      <div className="flex min-h-0 min-w-0 shrink-0 flex-col overflow-hidden" style={vert ? { height: firstSize ?? `${ratio * 100}%` } : { width: firstSize ?? `${ratio * 100}%` }}>
+        {a}
+      </div>
+      <div
+        role="separator"
+        aria-orientation={vert ? "horizontal" : "vertical"}
+        title="拖动调整；双击复位"
+        onPointerDown={(e) => {
+          e.preventDefault();
+          dragging.current = true;
+          document.body.style.cursor = vert ? "row-resize" : "col-resize";
+          document.body.style.userSelect = "none";
+        }}
+        onDoubleClick={() => setRatio(initialRatio)}
+        className={
+          vert
+            ? "group relative z-10 h-2 shrink-0 cursor-row-resize"
+            : "group relative z-10 w-2 shrink-0 cursor-col-resize"
+        }
+        style={{ background: "transparent" }}
+      >
+        <div
+          className={
+            vert
+              ? "absolute inset-x-0 top-1/2 h-px -translate-y-1/2 bg-[var(--border)] transition group-hover:h-1 group-hover:bg-[var(--accent)]"
+              : "absolute inset-y-0 left-1/2 w-px -translate-x-1/2 bg-[var(--border)] transition group-hover:w-1 group-hover:bg-[var(--accent)]"
+          }
+        />
+      </div>
+      <div className="flex min-h-0 min-w-0 flex-1 flex-col overflow-hidden">{b}</div>
+    </div>
+  );
+}