docs: advertise Agent Lightning skill

[Yuge Zhang (ultmaster)]

Summary

• advertise the Agent Lightning skill in the main README
• add a dedicated docs page with installation, workflow, and benchmark results
• add the page to the docs homepage and navigation

Verification

• uv run --locked --no-sync mkdocs build --strict
• git diff --check

[Copilot]

Pull request overview

This PR advertises the Agent Lightning skill across the repository’s primary entry points by adding a dedicated documentation page, wiring it into the MkDocs navigation, and linking it from the top-level README.

Changes:

• Added an “Agent Lightning Skill” section and install commands to the main README, plus a docs index entry.
• Introduced a new docs page describing installation, workflow, and benchmark results for the skill.
• Added the new page to MkDocs navigation and the docs homepage table.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
README.md	Adds prominent skill messaging, install commands, and a docs link from the repo landing page.
mkdocs.yml	Adds the new skill page to the documentation navigation.
docs/README.md	Adds the skill page to the docs homepage “Getting Started” table.
docs/10-agent-lightning-skill.md	New dedicated documentation page covering install, workflow, and measured results.

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