Add an opt-in benchmark probe and JSON runner that separate solve, construction, validation, and rendering time. Record stable search counters, environment metadata, warm-up and repetition policy, timeouts, errors, median spread, and instrumentation overhead.
Compile production solving without counters and interleave counted and plain trials when measuring overhead. Keep heavyweight cases outside the default correctness path while testing counter and report behavior cheaply.
Tests: Debug and Release CTest suites (7 passed each)
Refs: #8
Establish a CTest harness before changing solver behavior. Validate board dimensions, multiplicities, bounds, overlap and coverage against independent placement data, including known order-8 and constructed order-9 fixtures.
Document Debug and sanitizer workflows while keeping the defects tracked by #7 and #14 separate. Prepare a result adapter so the feasible solver regression can be enabled with the completion fix.
Tests: Release, ASan and UBSan CTest suites (3 passed each)
Refs: #1
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mgrettondann