fix(composer): no LaTeX conversion inside a typed markdown fence or backtick span (#184 O3)

In markdown mode each paragraph line is serialised before parseBlockMD
joins them, so $x$ inside a ``` fence became data-mx-maths markup
inside the resulting <pre><code> (rendered as math in a code block).
Track fence state across lines and skip math for fenced lines and for
backtick code spans. Unit tests added; verified in the browser.

Also: scripts/dev-homeserver.sh enables MSC4140 delayed events so
scheduled messages work locally.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/components/editor/output.test.ts

@@ -65,3 +65,27 @@ test('no math conversion inside a code block', () => {
 test('a message with no math is unchanged', () => {
   assert.equal(toMatrixCustomHTML(txt('just hello'), OPTS), 'just hello');
 });
+
+// Gitea #184 O3 — markdown mode: fences and backtick spans typed as plain
+// paragraphs are literal too (the block markdown parser only sees the fence
+// after the lines are joined, so math must be skipped while serialising them).
+const MD_OPTS = { ...OPTS, allowInlineMarkdown: true, allowBlockMarkdown: true };
+
+test('markdown: no math conversion inside a typed ``` fence', () => {
+  const paragraphs = [
+    el(BlockType.Paragraph, [txt('```')]),
+    el(BlockType.Paragraph, [txt('$x$ literal')]),
+    el(BlockType.Paragraph, [txt('```')]),
+    el(BlockType.Paragraph, [txt('after $y$')]),
+  ];
+  const out = toMatrixCustomHTML(paragraphs, MD_OPTS);
+  assert.ok(out.includes('<pre'), 'fence became a code block');
+  assert.ok(out.includes('$x$ literal'), 'code block content stays literal');
+  assert.ok(out.includes('data-mx-maths="y"'), 'math after the fence still converts');
+});
+
+test('markdown: no math conversion inside a backtick span, math outside still converts', () => {
+  const out = toMatrixCustomHTML(el(BlockType.Paragraph, [txt('use `$x$` and $y$')]), MD_OPTS);
+  assert.ok(/<code[^>]*>\$x\$<\/code>/.test(out), 'backtick span stays literal');
+  assert.ok(out.includes('data-mx-maths="y"'));
+});