[aleksUIX]

Follow-up to #4671, targeting its feature branch.

The original-seat refactor removes existing null bid-list checks in 50 adapters. If one seat omits bid or supplies bid: null, the adapter throws instead of returning valid sibling bids. This restores those guards and retains the originating seat on surviving bids.

Six regression tests use real JSON decoding and the public makeBids methods in Aax, Adelement and Aja. They check mixed malformed/valid seats, empty responses, and preservation of the valid bid and its originalSeat.

Validation:

• All six new tests throw NullPointerException on the original Preserve original OpenRTB seat in bid metadata #4671 head, 65e16545a.
• With the fix, the complete root Maven test run passes: 8,893 passed, two skipped, zero failures or errors across 909 suites. This includes all six regressions.
• Checkstyle reports zero violations. All 50 changed production lines execute in that run. Both predicate outcomes are exercised in the three regression adapters.
• Separate Docker-backed functional modules and live bidders were not exercised.