Add semantic headings to stepper component

docs/syntax/stepper.md

@@ -6,14 +6,12 @@ to break down processes into manageable stages.
 By default every step title is a link with a generated anchor.
 But you can override the default anchor by adding the `:anchor:` option to the step.
 
-## Basic Stepper
+## Basic stepper
 
 :::::::{tab-set}
 ::::::{tab-item} Output
 :::::{stepper}
 
-:::::{stepper}
-
 ::::{step} Install
 First install the dependencies.
 ```shell
@@ -77,7 +75,7 @@ npm run test
 
 :::::::
 
-## Advanced Example
+## Advanced example
 
 :::::::{tab-set}
 
@@ -203,3 +201,27 @@ To see how dynamic mapping works, add a new document to the `books` index with a
 ::::::
 
 :::::::
+
+## Table of contents integration
+
+Stepper step titles automatically appear in the page's "On this page" table of contents (ToC) sidebar, making it easier for users to navigate directly to specific steps.
+
+### Nested steppers
+
+When steppers are nested inside other directive components (like `{tab-set}`, `{dropdown}`, or other containers), their step titles are **not** included in the ToC to avoid duplicate or competing headings across multiple tabs or links to content that might be collapsed or hidden.
+
+**Example of excluded stepper:**
+```markdown
+::::{tab-set}
+:::{tab-item} Tab 1
+::{stepper}
+:{step} This step won't appear in ToC
+Content here...
+:
+::
+:::
+::::
+```
+## Dynamic heading levels
+
+Stepper step titles automatically adjust their heading level based on the preceding heading in the document, ensuring proper document hierarchy and semantic structure.

src/Elastic.Markdown/IO/MarkdownFile.cs

@@ -14,6 +14,7 @@
 using Elastic.Markdown.Myst;
 using Elastic.Markdown.Myst.Directives;
 using Elastic.Markdown.Myst.Directives.Include;
+using Elastic.Markdown.Myst.Directives.Stepper;
 using Elastic.Markdown.Myst.FrontMatter;
 using Elastic.Markdown.Myst.InlineParsers;
 using Markdig;
@@ -263,22 +264,50 @@ public static List<PageTocItem> GetAnchors(
 			.ToArray();
 
 		var includedTocs = includes.SelectMany(i => i!.TableOfContentItems).ToArray();
-		var toc = document
+
+		// Collect headings from standard markdown
+		var headingTocs = document
 			.Descendants<HeadingBlock>()
 			.Where(block => block is { Level: >= 2 })
-			.Select(h => (h.GetData("header") as string, h.GetData("anchor") as string, h.Level))
+			.Select(h => (h.GetData("header") as string, h.GetData("anchor") as string, h.Level, h.Line))
 			.Where(h => h.Item1 is not null)
 			.Select(h =>
 			{
 				var header = h.Item1!.StripMarkdown();
-				return new PageTocItem
+				return new
 				{
-					Heading = header,
-					Slug = (h.Item2 ?? h.Item1).Slugify(),
-					Level = h.Level
+					TocItem = new PageTocItem
+					{
+						Heading = header,
+						Slug = (h.Item2 ?? h.Item1).Slugify(),
+						Level = h.Level
+					},
+					h.Line
 				};
-			})
-			.Concat(includedTocs)
+			});
+
+		// Collect headings from Stepper steps
+		var stepperTocs = document
+			.Descendants<DirectiveBlock>()
+			.OfType<StepBlock>()
+			.Where(step => !string.IsNullOrEmpty(step.Title))
+			.Where(step => !IsNestedInOtherDirective(step))
+			.Select(step => new
+			{
+				TocItem = new PageTocItem
+				{
+					Heading = step.Title,
+					Slug = step.Anchor,
+					Level = step.HeadingLevel // Use dynamic heading level
+				},
+				step.Line
+			});
+
+		var toc = headingTocs
+			.Concat(stepperTocs)
+			.Concat(includedTocs.Select(item => new { TocItem = item, Line = 0 }))
+			.OrderBy(item => item.Line)
+			.Select(item => item.TocItem)
 			.Select(toc => subs.Count == 0
 				? toc
 				: toc.Heading.AsSpan().ReplaceSubstitutions(subs, set.Context.Collector, out var r)
@@ -301,6 +330,18 @@ public static List<PageTocItem> GetAnchors(
 		return toc;
 	}
 
+	private static bool IsNestedInOtherDirective(DirectiveBlock block)
+	{
+		var parent = block.Parent;
+		while (parent is not null)
+		{
+			if (parent is DirectiveBlock { } otherDirective && otherDirective != block && otherDirective is not StepperBlock)
+				return true;
+			parent = parent.Parent;
+		}
+		return false;
+	}
+
 	private YamlFrontMatter ProcessYamlFrontMatter(MarkdownDocument document)
 	{
 		if (document.FirstOrDefault() is not YamlFrontMatterBlock yaml)

src/Elastic.Markdown/Myst/Directives/DirectiveHtmlRenderer.cs

@@ -124,7 +124,8 @@ private static void WriteStepBlock(HtmlRenderer renderer, StepBlock block)
 		{
 			DirectiveBlock = block,
 			Title = block.Title,
-			Anchor = block.Anchor
+			Anchor = block.Anchor,
+			HeadingLevel = block.HeadingLevel
 		});
 		RenderRazorSlice(slice, renderer);
 	}

src/Elastic.Markdown/Myst/Directives/Stepper/StepView.cshtml

@@ -2,11 +2,39 @@
 <li class="step">
 	@if (!string.IsNullOrEmpty(Model.Title))
 	{
-		<p id="@Model.Anchor">
-			<a class="title" href="#@Model.Anchor">
-				@Model.Title
-			</a>
-		</p>
+		@switch (Model.HeadingLevel)
+		{
+			case 1:
+				<h1 id="@Model.Anchor">
+					<a href="#@Model.Anchor">@Model.Title</a>
+				</h1>
+				break;
+			case 2:
+				<h2 id="@Model.Anchor">
+					<a href="#@Model.Anchor">@Model.Title</a>
+				</h2>
+				break;
+			case 3:
+				<h3 id="@Model.Anchor">
+					<a href="#@Model.Anchor">@Model.Title</a>
+				</h3>
+				break;
+			case 4:
+				<h4 id="@Model.Anchor">
+					<a href="#@Model.Anchor">@Model.Title</a>
+				</h4>
+				break;
+			case 5:
+				<h5 id="@Model.Anchor">
+					<a href="#@Model.Anchor">@Model.Title</a>
+				</h5>
+				break;
+			default:
+				<h6 id="@Model.Anchor">
+					<a href="#@Model.Anchor">@Model.Title</a>
+				</h6>
+				break;
+		}
 	}
 	@Model.RenderBlock()
 </li>

src/Elastic.Markdown/Myst/Directives/Stepper/StepViewModel.cs

@@ -8,4 +8,5 @@ public class StepViewModel : DirectiveViewModel
 {
 	public required string Title { get; init; }
 	public required string Anchor { get; init; }
+	public required int HeadingLevel { get; init; }
 }

src/Elastic.Markdown/Myst/Directives/Stepper/StepperBlock.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information
 
 using Elastic.Markdown.Helpers;
+using Markdig.Syntax;
 
 namespace Elastic.Markdown.Myst.Directives.Stepper;
 
@@ -20,10 +21,48 @@ public class StepBlock(DirectiveBlockParser parser, ParserContext context) : Dir
 	public override string Directive => "step";
 	public string Title { get; private set; } = string.Empty;
 	public string Anchor { get; private set; } = string.Empty;
+	public int HeadingLevel { get; private set; } = 3; // Default to h3
 
 	public override void FinalizeAndValidate(ParserContext context)
 	{
 		Title = Arguments ?? string.Empty;
 		Anchor = Prop("anchor") ?? Title.Slugify();
+
+		// Calculate heading level based on preceding heading
+		HeadingLevel = CalculateHeadingLevel();
+
+		// Set CrossReferenceName so this step can be found by ToC generation
+		if (!string.IsNullOrEmpty(Title))
+		{
+			CrossReferenceName = Anchor;
+		}
+	}
+
+	private int CalculateHeadingLevel()
+	{
+		// Find the document root
+		var current = (ContainerBlock)this;
+		while (current.Parent != null)
+			current = current.Parent;
+
+		// Find all headings that come before this step in document order
+		var allBlocks = current.Descendants().ToList();
+		var thisIndex = allBlocks.IndexOf(this);
+
+		if (thisIndex == -1)
+			return 3; // Default fallback
+
+		// Look backwards for the most recent heading
+		for (var i = thisIndex - 1; i >= 0; i--)
+		{
+			if (allBlocks[i] is HeadingBlock heading)
+			{
+				// Step should be one level deeper than the preceding heading
+				return Math.Min(heading.Level + 1, 6); // Cap at h6
+			}
+		}
+
+		// No preceding heading found, default to h2 (level 2)
+		return 2;
 	}
 }