Fixes Next.js session management and multiple bugfixes and improvements

This release fixes critical issues with authentication persistence in Next.js, session management errors, and the @mention dropdown functionality, while also improving performance by reducing unnecessary API requests.

• Adds a workaround for a bug where session was not persisted across reloads in studios embedded in Next.js, and would result in an error message Session with sid (…) not found.
• Reduces number of requests with tag sanity.studio.history-revision after editing documents.
• Restores the behavior where asset sources receive the current asset in selectedAssets when opened via the browse flow, even when the field already has a value.
• Fixes an issue causing authentication to not persist between page reloads in Next.js.
• Fixes an issue where the @mention dropdown in comments might show “No users found” when any system.group document had members: null.
• Fixes virtualization issues using the dialog and renderDefault.

• The debug command has an improved output format and can now be run outside a project.
• init has improve flags.
• Many commands now has plural names, with aliases for the singular versions.
• Deprecated start command. Use preview instead.
• Adds support for non-interactive mode for app templates.
• Load all env vars for schema extract.
• Prevent duplicate deprecation warnings during sanity deploy.
• Schema extract path always appends schema.json.
• Fixes an issue where import command required --token flag.