Hydrate the released UI RC required by active browser guarantees

[adrianwebb]

Problem

Admin declared a broad compatible UI prerelease range, but its lockfile retained @treeseed/ui 0.12.18-rc.5 after the redirect-toast behavior landed in 0.12.18-rc.6. The packed/managed Admin therefore lost the successful self-leave toast even though the UI source and declared range were compatible.

Acceptance

• Pin the minimum UI prerelease that supplies the catalogued redirect-toast contract.
• Regenerate the lockfile from published artifacts and prove the installed dependency is rc.6 or newer.
• Pass independent release verification.
• Pass the exact 20-scene authentication/account/team graph through the manager-owned canonical hostname in a live development session before publishing the Admin RC.

This is a dependency-hydration failure, not an accepted browser behavior.