Puzzles
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Seam: Horseman and colormap use named variables and solve answers.
The concurrent conjunction difference from PAKCS remains pinned (#139).

Run ./run after make stage, or run unit_boundary.py from tests/.
The run script selects the staged Python and the session backend.
expected.out records stdout; stderr is shown on failure by the test.
The driver comments explain the individual probes and their order.
The corpus README.md lists the backends and the oracle for this driver.
