Linear TV: book and report position in break (first/last in break) #8009

Problem

Linear TV buyers pay extra for where a spot sits inside a commercial break: first in break, second, second-to-last, last. In the Netherlands these "preferred positions" (A1, A2, E1, E2 in the industry tool) are a standard surcharged option at every sales house. The same idea exists in most TV markets and in radio.

AdCP can't express any of this:

• Booking. A buyer cannot ask for a position, and a product cannot offer one or price it.
• Reporting. by_spot[] (3.2) reports spot_id, aired_at, network, station, daypart and creative_id, but not where in the break the spot aired. A buyer cannot check that a surcharged position was delivered.

The only related things in the schema are the POD_POSITION creative macro and DOOH loop_position. Neither is a booking or reporting field. I found no open issue for this. #5686 covers a placement taxonomy for print, which is the closest analogue.

Proposed shape

1. Reporting. Add optional break_position to by_spot[] items:

   • position_in_break (integer, 1-based)
   • spots_in_break (integer)
   • break_id (optional string)

   That lets a buyer derive first or last without a market-specific enum.

2. Booking. Let a product declare position options a buyer can select (first, second, second_last, last, plus any), and price them through the price-adjustment mechanism in RFC: declare price adjustments for buyer-selectable product dimensions #7659 rather than a new pricing model.

3. Capability. spot_reporting.available_fields (or similar) declares whether the seller reports break position, so buyers don't treat a missing field as "not delivered".

Relationship to other work

• Linear TV: preemption notice + replacement offer / accept-reject workflow #5683 adds spot_status and makegood linkage to by_spot[]. Break position should land in the same item shape.
• RFC: declare price adjustments for buyer-selectable product dimensions #7659 gives the pricing mechanism.
• Print: shared placement/position taxonomy (cover positions, section, page) #5686 is the print position taxonomy. Worth checking whether one shared position vocabulary covers both.

Milestone: 3.3.0. The reporting half is small and doesn't depend on the booking half.