Faster Structure Tool intent resolution, and bugfixes

Document links no longer wait for the structure tool to find the document's place in a slow custom structure. The document opens first, and the lists fill in around it.

• The releases and variants pickers move into the navigation drawer on small screens, so the navbar stays usable on mobile.
• Studio no longer logs "WebSocket connection to '…' failed: Page entered Back-Forward Cache" when you navigate away, and presence works on a page restored with the browser's back button.
• @sanity/validation no longer reports references between documents in the same release as unpublished, and exports withReleaseReferences for custom getDocumentExists implementations. The requirePublishedReferences argument of useValidationStatus, useSetImmediateValidation and DocumentStore.pair.validation is deprecated and ignored.
• Release actions no longer report a missing permission after a dry run fails for another reason, such as reaching the plan release limit. Publish and Schedule are now disabled when the user can't publish one of the release's documents.
• Fixed url fields with Rule.uri({relativeOnly: true}) showing invalid styling on valid relative URLs.
• New sanity context mcp commands list, inspect, create, update, delete and check Context MCP endpoints. update and delete refuse endpoints a blueprint manages.
• The workspace release limit now also applies to creating a release from the Releases tool, duplicating a release, and reverting a release.
• useIntentLink and IntentLink can now omit params. The link resolves to /intent/<name>, and intent handling treats the missing params as an empty object.