Deprovision Organization Channels

Soft-delete an offboarded organization's live channels (agent links, region rows and number bindings go with them, each audited).

Separate from the platform flag, which is a pause: the org must already be off the agent platform, and no unpaused agent may still be linked to its channels. Defaults to a dry run listing what would go; POST {"dry_run": false} to apply. Re-runnable.

The numbers stay leased — only their messaging bindings are cleared, so they return to the eligible pool. A channel reported with has_messaging_number: false is the only record of that number on our side; note it down before applying.