Remove sample identities from the repository; document the rule

Datasets may be confidential; sample names and measured unit cells committed to
the repo can leak outside the group working on them. Scrub existing occurrences
and add a "No sample identities in the repository" section to CLAUDE.md
(forbidden: sample/dataset names, internal codes, measured cells tied to a
sample; fine: space group / lattice / twinning descriptors).

- Comments: replace internal dataset codes and protein names with the
  crystallographic situation they illustrate (centred vs pseudo-symmetric,
  holohedral, cubic, F-cubic/hexagonal, ...).
- Docs: same, in the analysis/writer/stream references and example configs.
- Tests: rename sample-named identifiers, TEST_CASE names, file prefixes and
  asserted labels to neutral crystallographic names (e.g. tetragonal_uc);
  behaviour unchanged. Reduce the CrystFEL reference PDB to a bare CRYST1 cell
  file (cell.pdb) and rename the reference data file.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/RugnuxTest.cpp

@@ -151,7 +151,7 @@ TEST_CASE("RugnuxCommandLine_Full", "[process]") {
     config.rotation_indexing_image_count = 30;
     config.spot_finding = DiffractionExperiment::DefaultDataProcessingSettings();
 
-    const std::string cmd = RugnuxCommandLine(config, x, "/data/lyso_master.h5");
+    const std::string cmd = RugnuxCommandLine(config, x, "/data/test_master.h5");
     CHECK(cmd.rfind("rugnux", 0) == 0);
     CHECK(cmd.find("-N 8") != std::string::npos);
     CHECK(cmd.find("-e 500") != std::string::npos);
@@ -162,7 +162,7 @@ TEST_CASE("RugnuxCommandLine_Full", "[process]") {
     // would not re-parse (getopt would leave 30 as a positional and drop the count).
     CHECK(cmd.find("-R30") != std::string::npos);
     CHECK(cmd.find("-R 30") == std::string::npos);
-    CHECK(cmd.find("/data/lyso_master.h5") != std::string::npos);
+    CHECK(cmd.find("/data/test_master.h5") != std::string::npos);
 }
 
 TEST_CASE("RugnuxCommandLine_AzInt", "[process]") {