test: the format and ASCII rules stop being a habit, and the stated sizes stop drifting

libavr's guidance binds this repo too, and until now nothing here checked it -
`ctest` runs `libavr_format_test()` over this tree's own sources now (rules 11
and 33), skipping rather than passing where clang-format is absent. It caught
drift on its first run: a file written this week and edited after formatting.

Where the README states a measured size, `libavr_size_claim_test()` holds it to
the image and holds the image to the prose: advancing the library pin moved
three of these across the fleet with nothing saying so, and re-recording one
now requires the sentence that quotes it to move too.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CMakeLists.txt

@@ -15,6 +15,7 @@ if(NOT EXISTS ${LIBAVR_ROOT}/CMakeLists.txt)
 	message(FATAL_ERROR "libavr not found at ${LIBAVR_ROOT} - run: git submodule update --init libavr")
 endif()
 add_subdirectory(${LIBAVR_ROOT} libavr-build)
+include(${LIBAVR_ROOT}/cmake/checks.cmake)
 
 add_executable(fantemp src/main.cpp)
 target_link_libraries(fantemp PRIVATE libavr)

test/CMakeLists.txt

@@ -1,3 +1,5 @@
+libavr_format_test()
+
 # The battery is a compile: a static_assert that fails is the failure. It is a
 # target rather than only a ctest so a plain build catches a regression too.
 add_library(consteval_tests OBJECT consteval.cpp)

test/consteval.cpp

@@ -58,9 +58,9 @@ static_assert(curve_rises());
 // definition puts that count at the nominal temperature.
 using app::thermistor::detail::quarters_entry;
 
-inline constexpr std::int32_t nominal_count = static_cast<std::int32_t>(
-    app::thermistor::adc_full_scale * app::thermistor::nominal_resistance /
-    (app::thermistor::series_resistor + app::thermistor::nominal_resistance));
+inline constexpr std::int32_t nominal_count =
+    static_cast<std::int32_t>(app::thermistor::adc_full_scale * app::thermistor::nominal_resistance /
+                              (app::thermistor::series_resistor + app::thermistor::nominal_resistance));
 static_assert(quarters_entry(nominal_count / 4) >= 100);    // 25.00 C, in quarters
 static_assert(quarters_entry(nominal_count / 4 + 1) < 100); // and the step below it