fix: tighten Dashboard and OpenAPI documentation

[cursor]

Findings

Broken

• None.

Wrong

• Separate the Plans and Billing Dashboard destinations.
• Mark the deprecated single-file download endpoint explicitly and direct new integrations to the batch endpoint.

Polish

• Use exact Dashboard navigation labels and breadcrumbs.
• Restore required reference-description endings for API keys and webhooks.
• Preserve Project and Organization product-term casing in affected OpenAPI summaries and generated pages.

Verification

• Installed and probed current stable packages in a fresh npm project: gt@2.16.3, generaltranslation@9.1.1, gt-next@11.1.5, gt-react@11.1.5, and gt-node@1.0.12.
• Confirmed there were no gt commits or stable package releases in the audit window.
• Regenerated OpenAPI pages and confirmed a clean diff.
• Passed all content validator tests, TypeScript checks, callout checks, reference-link checks, structure checks, unsafe-HTML checks, and link validation.
• Passed the 460-page production documentation build.