ink.branchline.publishSeed

Gift a seed. The caller must be signed in and must be the grantee of `grantor`; publishing passes that seed's planting right on to `grantee` as a new child seed. The AppView writes an ink.branchline.seed record to the caller's PDS and mirrors it into the local read cache. Root (grantor-less) seeds are not created through this endpoint — they are authored only by the branchline.ink repo.