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/lib/inlineShortcodes.test.ts

@@ -0,0 +1,80 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import {
+  isValidColorValue,
+  splitInlineShortcodes,
+} from "./inlineShortcodes.ts";
+
+describe("isValidColorValue", () => {
+  it("放行 #hex 与英文颜色名", () => {
+    assert.equal(isValidColorValue("#e03131"), true);
+    assert.equal(isValidColorValue("#FFF"), true);
+    assert.equal(isValidColorValue("#ffffffff"), true);
+    assert.equal(isValidColorValue("tomato"), true);
+  });
+  it("拒绝注入向量与非法值", () => {
+    assert.equal(isValidColorValue("url(https://evil)", ), false);
+    assert.equal(isValidColorValue("red;padding:0"), false);
+    assert.equal(isValidColorValue("#GGG"), false);
+    assert.equal(isValidColorValue(""), false);
+  });
+});
+
+describe("splitInlineShortcodes", () => {
+  it("无短代码时返回 null", () => {
+    assert.equal(splitInlineShortcodes("普通文本 == 未闭合 [kbd]未闭合"), null);
+  });
+
+  it("==高亮==", () => {
+    assert.deepEqual(splitInlineShortcodes("前==高亮==后"), [
+      { type: "text", value: "前" },
+      { type: "mark", value: "高亮" },
+      { type: "text", value: "后" },
+    ]);
+  });
+
+  it("[kbd]", () => {
+    assert.deepEqual(splitInlineShortcodes("[kbd]Ctrl+C[/kbd]"), [
+      { type: "kbd", value: "Ctrl+C" },
+    ]);
+  });
+
+  it("[color=前景] 与 [bg=背景]", () => {
+    assert.deepEqual(splitInlineShortcodes("[color=#e03131]红字[/color]"), [
+      { type: "color", value: "红字", fg: "#e03131" },
+    ]);
+    assert.deepEqual(splitInlineShortcodes("[bg=#fff3bf]黄底[/bg]"), [
+      { type: "color", value: "黄底", bg: "#fff3bf" },
+    ]);
+  });
+
+  it("[color=前景 bg=背景] 组合", () => {
+    assert.deepEqual(splitInlineShortcodes("[color=#fff bg=#c92a2a]白字红底[/color]"), [
+      { type: "color", value: "白字红底", fg: "#fff", bg: "#c92a2a" },
+    ]);
+  });
+
+  it("非法颜色整段回退为原文（返回 null 表示无需改写）", () => {
+    assert.equal(splitInlineShortcodes("[color=url(https://evil)]x[/color]"), null);
+    assert.equal(splitInlineShortcodes("[bg=red;padding:0]x[/bg]"), null);
+  });
+
+  it("未闭合标记保持字面", () => {
+    assert.equal(splitInlineShortcodes("[color=#fff]未闭合"), null);
+  });
+
+  it("混合片段按顺序拆分", () => {
+    assert.deepEqual(splitInlineShortcodes("a==b==[kbd]C[/kbd]d"), [
+      { type: "text", value: "a" },
+      { type: "mark", value: "b" },
+      { type: "kbd", value: "C" },
+      { type: "text", value: "d" },
+    ]);
+  });
+
+  it("大小写不敏感", () => {
+    assert.deepEqual(splitInlineShortcodes("[KBD]Esc[/KBD]"), [
+      { type: "kbd", value: "Esc" },
+    ]);
+  });
+});