feat(desktop): embed BoosAPI Desktop client as a subproject

Vendor the rebranded BoosAPI Desktop client (Tauri + Vue) into metapi as
a monorepo subdirectory under desktop/. Source only — node_modules,
dist, Cargo target and the upstream .git history are excluded.

desktop/ keeps its own independent Cargo workspace (desktop/src-tauri
with crates/*); it is not part of the backend boosapi crate, so a
`cargo check` at the metapi root still compiles only the backend. Build
the desktop app from desktop/src-tauri per desktop/README.md.

Note: app icons are still placeholder assets pending the final BoosAPI
logo. The updater signing keys live outside the repo and are not
included.

desktop/libs/markstream-vue/test/custom-html-close-heading-same-line.test.ts

@@ -0,0 +1,24 @@
+import { getMarkdown, parseMarkdownToStructure } from 'stream-markdown-parser'
+import { describe, expect, it } from 'vitest'
+
+describe('custom html close followed by heading marker (same line)', () => {
+  const md = getMarkdown('custom-html-close-heading-same-line', { customHtmlTags: ['think'] })
+
+  it('parses the trailing "##" as a heading node (not plain text)', () => {
+    const markdown = `<think>让我思考一下</think>## 我是潮位站潮位预报智能体，\n专门负责为您提供镇海潮位站的潮位预报服务。`
+    const nodes = parseMarkdownToStructure(markdown, md, { customHtmlTags: ['think'], final: true }) as any[]
+
+    // The custom tag can be represented as a root node (html_block) or as an inline
+    // custom node wrapped in a paragraph depending on markdown-it tokenization.
+    const hasThinkRoot = nodes[0]?.type === 'think'
+    const hasThinkInline = nodes[0]?.type === 'paragraph'
+      && Array.isArray(nodes[0]?.children)
+      && nodes[0].children.some((c: any) => c?.type === 'think' && c?.loading === false)
+
+    expect(hasThinkRoot || hasThinkInline).toBe(true)
+
+    expect(nodes[1].type).toBe('heading')
+    expect(nodes[1].level).toBe(2)
+    expect(nodes[1].text).toContain('我是潮位站潮位预报智能体')
+  })
+})