test(e2e): port markdown_rendering.feature to playwright

[carl-codeorg]

Ports the Visiting an external markdown level with details tag scenario from markdown_rendering.feature to markdown-rendering.spec.ts.

The test covers dashboard's "external" level type, which renders authored markdown — including raw HTML like <details>/<summary> — directly into the level body via SafeMarkdown. It:

• Loads an external markdown level and confirms the level body's <details id="cool-list"> starts closed.
• Clicks the <summary> tag and confirms the details element opens (open attribute set).

This exercises SafeMarkdown's raw-HTML passthrough for interactive elements, not just text rendering — a regression here would mean authored <details>/collapsible content silently stops working across every course that uses it.

What's not ported

The feature's second scenario (Viewing a level with blockly embedded in instructions, tagged @eyes) asserts pixel-level visual parity against Applitools-approved baselines for Blockly embedded in level instructions. There's no equivalent visual-regression harness in this Playwright suite (playwright.config.ts's screenshot: 'only-on-failure' is a failure artifact, not a baseline-diff mechanism), so porting just the navigate + lab-ready wait would silently drop the scenario's actual assertion. This gap is documented in a comment at the top of the spec file; the scenario stays in Cucumber/Applitools for now.

Migration mechanics

• Original feature file is tagged @playwright so the Cucumber suite skips the ported scenario, avoiding duplicate coverage.
• Adds MarkdownLevel page object (markdown-level.ts) and extends LessonLevelPage (lesson-level-page.ts) with a shared navigateToLevel helper for lab-level URLs.
• Verified green under the repo's 5x/all-browser stress gate.

Links

JIRA

Testing story

Deployment notes

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