Heading anchors and optional table of contents

[SyNeto]

Goal

Generate stable anchor IDs on every heading and (optionally) a clickable table of contents at the top of long documents.

Why

GitHub does this automatically on the web. Reading the same file locally without anchors makes deep-linking and skimming harder.

Proposed approach

• For each `h1`–`h6`, generate a slug (lowercase, dashes, deduplicated like GitHub) and inject an `id` plus a hover-revealed `<a class="anchor" href="#slug">` icon — same pattern as github.com.
• Render a TOC at the top of the document.

Open questions

• TOC: always-on, opt-in via a marker like `[TOC]`, or floating sidebar?
• Slug algorithm: GitHub's exact rules (handles unicode, emoji, deduplication) vs the simpler default. Probably worth matching GitHub for consistency.

Constraints

• No CDN dependencies. Slug logic is small enough to write in-tree.

Acceptance criteria

• Every heading has a stable, unique `id`
• Hovering a heading shows an anchor link
• Clicking the anchor copies a sharable URL with `#slug`
• (If TOC implemented) TOC links navigate correctly within the page