Add markdown reports across Trackio

[abidlabs]

I added first-class markdown reports to Trackio end-to-end so users can log report objects, browse them in a new Reports UI page, and access them from the CLI.

This PR was authored with AI assistance, but I reviewed it myself.

[gradio-pr-bot]

🪼 branch checks and previews

•	Name	Status	URL
🦄	Changes	detected!	Details

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
trackio	minor

---

• Add markdown reports across Trackio

---

‼️ Changeset not approved. Ensure the version bump is appropriate for all packages before approving.

• Maintainers can approve the changeset by checking this checkbox.

Something isn't right?

• Maintainers can change the version label to modify the version bump.
• If the bot has failed to detect any changes, or if this pull request needs to update multiple packages to different versions or requires a more comprehensive changelog entry, maintainers can update the changelog file directly.

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[abidlabs]

Thanks @znation for the review!