Add Usability Issue Detection docs page

[abhi-motgi]

What does this PR do? What is the motivation?

Adds a new Product Analytics documentation page for Usability Issue Detection (Preview) and registers it in the Product Analytics sidebar navigation.

The page covers:

• Overview and the three issue categories (System failure, Slow performance, User confusion)
• Prerequisites (Session Replay + Product Analytics, and the session_replay_analysis_write permission)
• Triggering an analysis from a funnel or from the Usability page
• Viewing issues, issue details, and analysis history
• Data retention behavior
• Triaging issues (New, Reviewed, Resolved, Ignored)

Merge readiness

• Ready for merge

For Datadog employees:

• ⚠️ Your branch name MUST follow the <name>/<description> convention and include the forward slash (/). If you've already created your PR with an incorrect branch name, please rename your branch and open a fresh PR.
• 🤖 New: Comment with /review to run an automated check that catches common issues before a Documentation team member reviews your PR.

AI assistance

Used Claude (Cowork) to draft and iterate on the page from internal source docs, apply the Datadog docs style guide, place screenshots, and set up the nav entry. Content and structure reviewed and edited manually.

Additional notes

[github-actions]

Preview links (active after the build_preview check completes)

New or renamed files

• https://docs-staging.datadoghq.com/abhi-motgi/sr-usability-issue-detection/product_analytics/usability

[hestonhoffman]

Hello! I've created a docs ticket for this one. Someone will be along to review it soon!

[rtrieu]

/review

[github-actions]

🤖 Automated review by Claude. AI-generated; verify before acting.

Nice, clean addition. A few notes: the frontmatter is missing a description (used across other Product Analytics pages for SEO/AI ingestion), and a couple of clarity/hyphenation nits in the body. No blockers.

_{Reviewed a57710c27a07c7f7bc399622e696709e4000f456 — workflow run}

[rtrieu]

for the issue details image, let's use this version where the detailed page is highlighted and the main page is darkened so it's a bit easier to see:

Another option:

[rtrieu]

approving, but would recommend swapping one of the images before publishing