Anisotropy verdict: the directional limits are a second hypothesis beside the tensor

The verdict gated only deltaB_linear, the Debye-Waller part of the tensor, against the data set's own
systematic floor. A deficit that does not follow s^2 (a FLAT signature) can stop the signal far earlier
in one direction and still read NOT_DETECTED: one open-arm set reported directional limits of
3.18/3.18/2.14 A beside NOT_DETECTED. The cone limits (<I/sigma> = 2 in 20 deg cones) were computed but
never consulted.

Now each statement is decided on its own evidence and either establishes anisotropy:
- tensor: unchanged gate;
- directional limits: at the best direction's limit the weakest cone's <I/sigma> is below the best
  cone's by more than 3.5 of their joint standard error (both read linearly in s^2 between shell
  centres, as the limits are), the weakest limit is measured (not censored at the data edge), and the
  limits are at least 0.25 A apart - the spread the report already calls "noticeable".

Why the magnitude term: with the standard errors alone (the counting statistics of the cones) the
weakest cone is "significantly" below the best on 172 of 216 battery sets, down to limits 0.5% apart
(measured with a replica of ConeLimits on the a897b08 battery's merged data). The cones differ
systematically (multiplicity and coverage depend on direction), so significance alone made DETECTED
near-universal. A refusal (CANNOT_DETERMINE: dose ramp, short sweep, triclinic, no unmerged data) is not
overruled - its reasons bias the cones too - but now reports the measured directional limits.

Report: ANISOTROPY_DETECTED_BY (TENSOR/DIRECTIONAL/BOTH/NONE); developer keys for the two cones'
<I/sigma> and errors; the summary row names the test that carried the verdict, and CANNOT_DETERMINE
rows give the directional limits; the mmCIF verdict comment says so. Report only: no intensity, flag or
decision downstream reads the verdict (the French-Wilson prior uses the tensor regardless).

Measured (battery replica, 225 sets with limits): directional statement established on 95; 23
NOT_DETECTED -> DETECTED (directional ratio 1.14-1.59); of the 17 sets with ratio > 1.2 and an
uncensored weakest limit, 11 flip, 5 stay CANNOT_DETERMINE with limits reported, 1 (sparse, noisy
cones) stays NOT_DETECTED. ANISOTROPY warnings (spread > 0.5 A) appear on 6 more sets. Confirmed with
rugnux runs on the ci tier, those 17 and the private arm: p.hkl and MTZ data identical to the base
(e34a5fb88) on every set compared.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

image_analysis/WriteReflections.cpp

@@ -474,7 +474,7 @@ void WriteMmcifReflections(const std::vector<MergedReflection> &reflections,
                 out << "_reflns.jfjoch_aniso_significance     " << Fmt(an.significance, 2)
                     << "   # deltaB(linear) / floor\n";
             out << "_reflns.jfjoch_aniso_verdict          " << AnisotropyVerdictCode(an.verdict)
-                << "   # DETECTED / NOT_DETECTED / CANNOT_DETERMINE, at deltaB(linear)/floor > 3.5\n";
+                << "   # DETECTED / NOT_DETECTED / CANNOT_DETERMINE: deltaB(linear)/floor > 3.5, or the directional limits\n";
             for (int i = 0; i < 3; ++i)
                 if (std::isfinite(an.d_min_axis[i]))
                     out << "_reflns.jfjoch_aniso_d_min_" << (i + 1) << "          "