[aleksUIX]

#94 treats pricing[] as alternatives, while #115 adds seller fees as extra
rows and leaves derived_units unchanged. At USD 25 CPM, a USD 50,000 commitment
containing a USD 2,500 fee leaves USD 47,500 for media, or 1.9 million impressions.
Using the whole commitment as media instead implies USD 52,500 including the fee.

This adds focused wording for that fee basis and an executable discussion
profile. The 49 fixed vectors cover price selection, fee-inclusive spend,
unit commitments and budget bounds. The supporting calculator also exercises
the final-rate reading from #30 without reapplying option rate adjustments.

Floor composition and automatic acceptance remain separate decisions in #30.
The adapter preserves an explicitly accepted counter below a posted floor and
returns floor_check: not_checked. A successful calculation does not establish
seller acceptance, reserve inventory or authorize a commitment. Tax-inclusive
amounts, print adjustments and general mandatory-fee structures are outside
this limited profile.

The normative spec and field indexes are unchanged. If the fee wording is
adopted, the affected body, appendix and example updates should land together.

Validation: 49 vectors, existing appendix checks and YAML parsing pass. Four
deliberate arithmetic regressions fail the relevant vectors, including a
reintroduced floor veto on an already accepted counter.

Refs #94 and #115. Related: #30.

Member of the IAB Tech Lab Agentic Taskforce, commenting in a personal capacity.