tests: follow REPORT_VERSION to 2

80e10f51b added an anisotropy section to the result report and moved
REPORT_VERSION from 1 to 2, but left ResultReportTest asserting 1, so the
[Diagnostics] tag has been failing on this branch since that commit. The
assertion is the point of the test - a consumer greps that key - so it
follows the constant.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CHMmeM1d489zvNFT7ZMN2P

tests/ResultReportTest.cpp

@@ -68,7 +68,7 @@ TEST_CASE("ResultReport_Render", "[Diagnostics]") {
     const auto text = RenderResultReport("prefix", "in.h5", x, result);
 
     // The stable keys a consumer greps for.
-    CHECK(text.find("\nREPORT_VERSION= 1\n") != std::string::npos);
+    CHECK(text.find("\nREPORT_VERSION= 2\n") != std::string::npos);
     CHECK(text.find("\nOUTPUT_PREFIX= prefix\n") != std::string::npos);
     CHECK(text.find("\nINDEXING_RATE= 0.8700\n") != std::string::npos);
     CHECK(text.find("\nSPACE_GROUP_NUMBER= 96\n") != std::string::npos);