docs(site): add ado-aw audit reference page

[github-actions]

Summary

• Adds a full ado-aw audit reference page to the site, covering all accepted input formats, flags, output layout, report shape, cache behavior, and permission failure handling.
• Adds a ### audit entry to the CLI Commands page with a cross-reference to the new reference page.
• Adds "Audit" to the Reference sidebar in astro.config.mjs.

The audit command was added in #691 but was completely absent from the site. Users looking for how to audit a completed pipeline run had no site documentation to reference.

Changes

• site/src/content/docs/reference/audit.mdx: new reference page ported and expanded from docs/audit.md
• site/src/content/docs/setup/cli.mdx: added ### audit subsection with flag summary and link to the reference page
• site/astro.config.mjs: added { label: 'Audit', slug: 'reference/audit' } to the Reference sidebar

Accuracy checks

• All flags, defaults, and behaviors verified against docs/audit.md (canonical source of truth for the command).
• AuditData key table verified against docs/audit.md — no invented keys.
• Output layout verified against docs/audit.md layout section.

Validation

• cd site && npm ci && npm run build
• Build succeeded: 33 page(s) built (up from 32)
• Starlight links validator: "All internal links are valid."

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Created by the docs-writer workflow.

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