feat(assistant): split messages into prose and fenced code

Qt's markdown renders a fence but gives no per-block hook, so a copy
button per code block needs the fences found first. An unclosed fence is
open code, which is every fence while a reply streams; a fence inside a
list item keeps its indent out of the copied text.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/desktop/assistant/test_md.js b/desktop/assistant/test_md.js
new file mode 100644
index 0000000..030cdc9
--- /dev/null
+++ b/desktop/assistant/test_md.js
@@ -0,0 +1,51 @@
+// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// Run: node desktop/assistant/test_md.js
+// Md.js is a QML library, so its .pragma line is stripped before node
+// evaluates it.
+
+const fs = require("fs");
+const assert = require("assert");
+
+const src = fs.readFileSync(__dirname + "/Md.js", "utf8")
+    .replace(/^\.pragma library$/m, "");
+const { split } = new Function(src + "\nreturn { split };")();
+
+const prose = text => ({ kind: "prose", text });
+const code = (lang, text, open = false) => ({ kind: "code", lang, text, open });
+
+assert.deepStrictEqual(split(""), []);
+assert.deepStrictEqual(split("Just **prose**.\n\nTwo paragraphs."),
+                       [prose("Just **prose**.\n\nTwo paragraphs.")]);
+// One fence, with a language, between prose.
+assert.deepStrictEqual(split("Run:\n```bash\nls -l\n```\nDone."),
+                       [prose("Run:"), code("bash", "ls -l"), prose("Done.")]);
+// Two fences, no language, blank lines kept inside code.
+assert.deepStrictEqual(split("```\na\n\nb\n```\n```\nc\n```"),
+                       [code("", "a\n\nb"), code("", "c")]);
+// Streaming: an unclosed fence is open code.
+assert.deepStrictEqual(split("Here:\n```py\nprint(1)\npri"),
+                       [prose("Here:"), code("py", "print(1)\npri", true)]);
+assert.deepStrictEqual(split("```"), [code("", "", true)]);
+// Inline backticks are not a fence.
+assert.deepStrictEqual(split("Use `ls` or ``a`b``."), [prose("Use `ls` or ``a`b``.")]);
+// A fence in a list item: its indent is stripped from the code.
+assert.deepStrictEqual(split("1. Install:\n   ```sh\n   make\n     make install\n   ```\n2. Go"),
+                       [prose("1. Install:"), code("sh", "make\n  make install"), prose("2. Go")]);
+// A shorter or different closing run does not close the fence.
+assert.deepStrictEqual(split("````\n```\n~~~\n````"), [code("", "```\n~~~")]);
+// Tilde fences.
+assert.deepStrictEqual(split("~~~js\nx\n~~~"), [code("js", "x")]);
+// A closing fence with text after it is content, not a close.
+assert.deepStrictEqual(split("```\n``` not\n```"), [code("", "``` not")]);
+
+console.log("ok");