Set where a connected channel's imported history tokenises.

Imported channel history has no workspace — nothing is downloaded, so there is no container — and registration refuses until a destination exists (content_routes.register_content_for_revenue, 409 tokenise_destination_unset). This is the only thing that clears that refusal, and the last gate before a permanent on-chain allocation, so every fact is checked HERE rather than assumed from the client having rendered a filtered list of teams.

Changing a destination applies FORWARD ONLY. Content already registered carries its own copy of the destination it was minted under (contents_v2.tokenise_destination_mode / tokenise_team_id), and resolve_registration_destination reads that copy in preference to the credential. Nothing here touches contents_v2 — that copy is the record, and the split derived from it is already on-chain.