Create comment tasks

Creates one comment task or a partial-success batch of up to 200. Each accepted task costs 1 credit. The target is any public TikTok or Instagram video, including a third party's — that is the intended use — while the posting account must be one of your own delivered accounts and its platform must match the target's (COMMENT_PLATFORM_MISMATCH otherwise). Deduplicate locally on (saved_account_id, target URL, comment_text): two different Idempotency-Keys carrying the same comment bill twice. The saved account must be client-owned, manager-assigned, and allowed to execute tasks by TokPortal Coverage, unless it is permanently grandfathered. TokPortal locks and revalidates the account and Coverage before the accepted-task debit and all accepted inserts commit in one transaction. Rejected rows are never charged. Read credits_charged instead of calculating it from the request, and read meta.rejected_count and each row's reason rather than inferring success from the 201. Send an Idempotency-Key and reuse the same key, method, path, and body after an uncertain transport result so the completed response is replayed without a second charge.