Prepare an episode's table read (metered — TWO CALLS, price first).

Prepares the read of an episode whose cast is complete (Casting in the Writers Lab, or POST /story-projects/{projectId}/cast): charges its table-read credit — TABLE_READ_SHORT up to 60 pages, TABLE_READ_LONG above, the same price a job that adopts the screenplay reserves (GET /credits lists both) — and adds the read's scene sound effects and music, the media a Story API read gets. The Writers Lab's "Continue to Table Read" on Casting is the same operation, through the same server core. TWO CALLS: sent without confirmed it PRICES the preparation and changes nothing (status: quoted, quotedOnly: true, credits, balanceAfter, sufficient, and a note to show the writer; when sufficient is false the caller must not confirm); sent again with confirmed: true it charges and queues the media (status: queued). ONCE PER SCREENPLAY VERSION: a version already charged for its read, on any surface, answers status: prepared, and a read whose media is being made answers preparing — both free — so a retry never charges twice. A confirmed call the balance cannot cover is refused with 402 insufficient_credits and changes nothing. Refused before the price: 404 script_not_found (not the caller's screenplay), 409 cast_precondition_failed (details.reason: script_not_finalized for a draft, screenplay_coverage_before_cast when the version's screenplay coverage is under the bar and not acknowledged, still scoring, or missing, script_not_cast_ready for a cast that is not complete, with details.missing), 409 project_precondition_failed (the project gate is closed) and 409 voice_retired (a voice the read would speak was retired). Requires Idempotency-Key. Scope: artifact:publish.