fix(core): add unique heading IDs to Markdown for Outline compatibility

[saadpocalypse]

Description

Outline's documentation states that the id on an outline item should match the target heading element's id. While useOutlineFromMarkdown is provided to derive these outline IDs, the <Markdown> component never rendered id attributes on the headings it produced. As a result, clicking an Outline item changed the location.hash but never scrolled the page because document.getElementById(id) returned null.

This PR fixes the issue by generating unique heading IDs during Markdown rendering to match the output of useOutlineFromMarkdown, and attaches them to the rendered heading tags and components.heading overrides.

Changes

• Refactored packages/core/src/Outline/parseOutlineFromMarkdown.ts to import helper functions from the parser module, eliminating duplicated code.
• Exported the inlineText, slugify, and uniqueSlug functions from packages/core/src/Markdown/parser.ts.
• Updated the MarkdownComponents type interface in packages/core/src/Markdown/Markdown.tsx so custom heading component overrides can accept an optional id.
• Implemented a headingIdMap memo hook in the <Markdown> component and propagated resolved heading IDs to all rendered header tags and components.
• Ensured compliance with React's Rules of Hooks by defining the headingIdMap hook above the early-return conditional check for inline display mode.
• Added a colocated unit test in packages/core/src/Markdown/Markdown.test.tsx to verify headings are rendered with the correct unique ID attributes.

Verification

• Ran the core package tests using pnpm -F @astryxdesign/core test packages/core/src/Markdown/Markdown.test.tsx --run and verified all 56 tests passed successfully.
• Confirmed that heading elements are rendered with matching ID attributes, enabling smooth scrolling/hash navigation without custom slug overrides.

Resolves #4173

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Project	Deployment	Actions	Updated (UTC)
astryx	Ready	Preview, Comment	Jul 22, 2026 10:49am

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