feat: 品牌裁剪弹窗/Markdown 行内短代码与详情视频块等

新增：
- BrandCropModal 品牌图裁剪弹窗 + cropImage 工具
- Markdown 行内短代码（inlineShortcodes + remark 插件）
- MdDetails 折叠块、MdVideo 视频块组件
- directiveBlocks/inlineShortcodes 测试

其它：
- 聊天后端（handler/service chat）调整
- Markdown 渲染链路、编辑器、全局样式与品牌相关面板更新

frontend/components/markdown/remarkInlineShortcodes.ts

@@ -0,0 +1,58 @@
+import type { Root as MdastRoot } from "mdast";
+import type { Text } from "mdast";
+import { visit, SKIP } from "unist-util-visit";
+import { splitInlineShortcodes } from "@/lib/inlineShortcodes";
+
+const QUICK_RE = /==|\[(?:kbd|color|bg)[=\]]/i;
+
+type MdastParent = { children: Array<Record<string, unknown>>; type: string };
+
+/** 行内短代码 → mdast 节点（mdast-util-to-hast 支持 data.hName / data.hProperties） */
+function segToNodes(
+  seg: Exclude<ReturnType<typeof splitInlineShortcodes>, null>[number]
+): Record<string, unknown>[] {
+  if (seg.type === "text") return [{ type: "text", value: seg.value }];
+  if (seg.type === "mark" || seg.type === "kbd") {
+    return [
+      {
+        type: "emphasis",
+        data: { hName: seg.type },
+        children: [{ type: "text", value: seg.value }],
+      },
+    ];
+  }
+  const style = [
+    seg.fg ? `color:${seg.fg}` : null,
+    seg.bg ? `background-color:${seg.bg}` : null,
+  ]
+    .filter(Boolean)
+    .join(";");
+  return [
+    {
+      type: "emphasis",
+      data: { hName: "span", hProperties: { style } },
+      children: [{ type: "text", value: seg.value }],
+    },
+  ];
+}
+
+/**
+ * remark 插件：把文本节点中的 ==高亮== / [kbd] / [color] / [bg] 展开为
+ * mark/kbd/span 节点。code/inlineCode 是字面节点没有子文本，天然免疫；
+ * 未命中短代码的文本原样保留。
+ */
+export function remarkInlineShortcodes() {
+  return (tree: MdastRoot) => {
+    visit(tree, "text", (node: Text, index, parent) => {
+      const p = parent as unknown as MdastParent | null;
+      if (!p || index === undefined) return;
+      const value = node.value;
+      if (!QUICK_RE.test(value)) return;
+      const segs = splitInlineShortcodes(value);
+      if (!segs) return;
+      const nodes = segs.flatMap(segToNodes);
+      p.children.splice(index, 1, ...nodes);
+      return [SKIP, index + nodes.length];
+    });
+  };
+}