Readers: polarization from miniCBF and d*TREK headers (RESULT-CHANGING)

No reader parsed a polarization, and ApplyRugnuxExperimentDefaults then set
P = 0.99 (an undulator value) unconditionally, so laboratory-source data were
corrected as if from a synchrotron. Every d*TREK (Rigaku Saturn/A200) header in
the open arm states SOURCE_POLARZ=0.5 1 0 0, i.e. unpolarized; at Cu K-alpha and
2 A the wrong factor puts a +-33% azimuthal modulation on the intensities.

- d*TREK SMV: SOURCE_POLARZ is the fraction f followed by the plane normal (as
  dxtbx's FormatSMVRigaku reads it); stored as degree 2f - 1, negative where the
  normal lies along lab x (plane containing y).
- miniCBF: "# Polarization f" is the fraction in the horizontal plane; stored as
  2f - 1 ("None" or a missing line leave it unset).
- ApplyRugnuxExperimentDefaults sets 0.99 only where the file stated none;
  --polarization still overrides. ADSC SMV, marCCD and NXmx state nothing and
  keep 0.99.
- The "Header:" log line reports the stated polarization.

RESULT-CHANGING: d*TREK home-source sets (0.99 -> 0), one Rigaku miniCBF set
(0.99 -> 0), miniCBF sets stating 0.99 (0.99 -> 0.98).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PXc1zD1yxHqaR1DGdCTHL4

reader/MiniCBF.cpp

@@ -267,6 +267,8 @@ Header ParseHeader(const char *data, size_t size) {
     h.exposure_s     = Num(t, R"(#\s*Exposure_time\s+([\d.eE+-]+))");
     h.period_s       = Num(t, R"(#\s*Exposure_period\s+([\d.eE+-]+))");
     h.count_cutoff   = Int(t, R"(#\s*Count_cutoff\s+(\d+))");
+    if (Match(t, R"(#\s*Polarization\s+([\d.eE+-]+))").has_value())
+        h.polarization_fraction = Num(t, R"(#\s*Polarization\s+([\d.eE+-]+))");
     h.axis_name      = Match(t, R"(#\s*Oscillation_axis\s+(\S+))").value_or("omega");
     // "+SLOW" / "+FAST" on that same line: which of the image's two directions the spindle runs
     // along. Some writers state that instead of an axis name, and it is the only thing a header with