feat(tests): the sink is a cost fixture -- 23 hand-written costs disagree with HD, ratcheted

The 655-fixture corpus is HD-written, so a stated modifier BASECOST always
equals what HD recomputes -- hiding a real divergence, proved by mutation
(AOE BASECOST 9.75 moved HD's answer not at all): HD restores the stated
BASECOST and then setSelectedOption() overwrites it with the option's cost
(GenericObject.java:3665, :3747), where the engine lets _base_cost_from_xml
win. Plus AreaEffect's radius value math and DoT's template adders. The sink's
slot Force Fields gain the 6E PDLEVELS shape; a shrink-only cost ledger
(validation_sink_cost_gaps.json, 23 values, all reasoned) ratchets it all.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PrVDXgpDfQpzEGErZTLjEs

Author: pdbethke