Implement anchor directive component for wrapping content with custom IDs

[Copilot]

Implemented Anchor Directive Component

Successfully implemented the anchor directive component that allows wrapping content with a div containing a custom ID for linking purposes.

Implementation Progress:

• Create AnchorBlock.cs class inheriting from DirectiveBlock
• Add anchor directive parsing logic to DirectiveBlockParser.cs
• Add anchor HTML rendering logic to DirectiveHtmlRenderer.cs
• Create appropriate view file (AnchorView.cshtml) for HTML rendering
• Create view model (AnchorViewModel.cs) for the component
• Ensure anchors are properly registered for cross-referencing
• Create comprehensive tests for the anchor component
• Test both standalone anchors and anchors wrapping other components
• Verify linking functionality works correctly
• Run all tests to ensure no regressions
• Remove accidentally added dotnet-install.sh file
• Fix AnchorId nullability and remove unnecessary fallback

Key Features Implemented:
✅ Syntax Support: ::::{anchor} custom-id
✅ Content Wrapping: Wraps any inner content with a div containing id="custom-id"
✅ Argument Validation: Emits proper error if ID argument is missing
✅ ID Slugification: Automatically converts spaces to hyphens (e.g., "Custom ID" → "custom-id")
✅ Cross-Reference Support: Sets CrossReferenceName for linking capabilities
✅ HTML Generation: Renders as <div id="custom-id">...content...</div>
✅ Error Handling: Provides clear diagnostics for invalid usage
✅ Non-nullable Design: AnchorId is always set to a valid string value

Example Usage:

::::{anchor} custom-id

:::{dropdown} Dropdown Title
Dropdown content
:::

::::

Link to [custom anchor](#custom-id).

Generated HTML:

<div id="custom-id">
  <details class="dropdown">
    <summary>Dropdown Title</summary>
    <div>Dropdown content</div>
  </details>
</div>

All tests pass and the component integrates seamlessly with existing directive infrastructure.

Fixes #1909.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[github-actions]

Label error. Requires exactly 1 of: automation, breaking, bug, changelog:skip, chore, ci, dependencies, documentation, enhancement, feature, fix, redesign. Found:

[reakaleek]

@copilot remove this file

[Copilot]

Removed the accidentally added dotnet-install.sh file. This was a development artifact that shouldn't have been committed. Fixed in df5236c.

[reakaleek]

LGTM