docs(status): classify conditional Clay reduction status

[inaciovasquez2020]

Classifies clay-problem-lab as Conditional Clay-Problem Reduction Lab while project-defined axioms remain.

Verified:

• scripts/check_conditional_clay_status.py passes
• pytest passes

Boundary:

• This does not prove or close any Clay problem.
• This treats project axioms as trusted assumptions, not proofs.
• The repository may test cleanly, but theorem-level Clay closure is not asserted while 2 axioms remain.