fix: Fixed issues with the deflist plugin and TOC builder

markdown/toc_test.odin

@@ -0,0 +1,35 @@
+#+test
+package markdown
+
+import "core:strings"
+import "core:testing"
+
+@(test)
+test_toc_sequential_nesting :: proc(t: ^testing.T) {
+	html := `<h1 id="a">A</h1><h2 id="b">B</h2><h1 id="c">C</h1>`
+	result := generate_toc(html, context.temp_allocator)
+	testing.expect(t, strings.contains(result, `<a href="#a">A</a>`))
+	testing.expect(t, strings.contains(result, `<a href="#b">B</a>`))
+	testing.expect(t, strings.contains(result, `<a href="#c">C</a>`))
+	// A well-formed list never places a <ul> directly inside a <ul>.
+	testing.expect(t, !strings.contains(result, "<ul>\n<ul>"))
+}
+
+// Regression: a heading level that jumps by more than one (h1 -> h3) must not
+// emit stacked, parentless <ul> tags. Each skipped level is wrapped in an <li>
+// so the list stays valid.
+@(test)
+test_toc_level_jump_stays_valid :: proc(t: ^testing.T) {
+	html := `<h1 id="a">A</h1><h3 id="b">B</h3>`
+	result := generate_toc(html, context.temp_allocator)
+	testing.expect(t, !strings.contains(result, "<ul>\n<ul>"))
+	// The intermediate level is hosted by an <li>.
+	testing.expect(t, strings.contains(result, "<li>\n<ul>"))
+	testing.expect(t, strings.contains(result, `<a href="#b">B</a>`))
+}
+
+@(test)
+test_toc_empty_when_no_headings :: proc(t: ^testing.T) {
+	result := generate_toc("<p>no headings here</p>", context.temp_allocator)
+	testing.expect_value(t, result, "")
+}