docs: sync SVG, SSO, and OpenAPI behavior

[cursor]

Findings

Broken

• None. Link, structure, unsafe-HTML, callout, reference-link, and production-build checks pass.

Wrong

• Document the shipped SVG file format across Core upload and enqueue APIs, Dashboard review behavior, asynchronous layout processing, and usage metering.
• Sync the public OpenAPI snapshot with runtime standard actions and the current JSON-value and model-provider schemas.
• Document the exact IdP entity ID now required by manual SAML configuration.

Polish

• Remove a hand-authored Next steps section already covered by related.links.
• Normalize recently added Vue metadata descriptions to sentence case.

Verification

• Installed and probed @generaltranslation/api@0.0.2, generaltranslation@9.1.9, and gt@2.17.2 in a clean project; the published FileFormat accepts SVG, SVG remains UTF-8 text, and only LOTTIE is binary.
• Installed and inspected gt-vue@0.1.3 and gt-rrweb@0.2.0; their public runtime exports match the recent reference docs.
• Ran all content validators and validator tests.
• Built all 509 static pages successfully. Fumadocs logged non-fatal TypeScript-schema generation warnings for the newly recursive JSON-value schema while completing the build.