bench: add repeatable solver measurements

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

CMakeLists.txt

@@ -6,6 +6,12 @@ set(CMAKE_CXX_STANDARD 20)
 add_executable(partridge_cpp
         main.cc)
 
+option(PARTRIDGE_BUILD_BENCHMARKS "Build the heavyweight benchmark probe" OFF)
+if(PARTRIDGE_BUILD_BENCHMARKS)
+  add_executable(partridge_benchmark
+          benchmarks/benchmark.cc)
+endif()
+
 include(CTest)
 
 if(BUILD_TESTING)
@@ -16,4 +22,11 @@ if(BUILD_TESTING)
   add_test(NAME rendering COMMAND partridge_tests rendering)
   add_test(NAME solver-small COMMAND partridge_tests solver-small)
   add_test(NAME solver-completion COMMAND partridge_tests solver-completion)
+  add_test(NAME search-counters COMMAND partridge_tests search-counters)
+  find_package(Python3 COMPONENTS Interpreter)
+  if(Python3_Interpreter_FOUND)
+    add_test(NAME benchmark-format
+      COMMAND "${Python3_EXECUTABLE}" "${CMAKE_CURRENT_SOURCE_DIR}/benchmarks/run.py"
+              --self-test)
+  endif()
 endif()