[Fix] Improve rank-deficient detection and bump odrpack to >=0.5

Fix incorrect ODRPACK95 info code parsing: rank deficiency is encoded
in the tens digit (info // 10 % 10), not the hundreds digit. Add
irank and inv_condnum to the warning message for diagnostics.

pyerrors/fits.py

@@ -670,13 +670,17 @@ def total_least_squares(x, y, func, silent=False, **kwargs):
         print('Residual variance:', output.residual_variance)
 
     if not out.success:
-        # info % 5 gives the convergence status: 1=sum-of-sq, 2=param, 3=both
-        # If odrpack reports rank deficiency (e.g. vanishing chi-squared when
-        # n_obs == n_parms), convergence was still achieved – allow with a warning.
-        if out.info % 5 in [1, 2, 3]:
+        # ODRPACK95 info code structure (see User Guide §4):
+        #   info % 10        -> convergence: 1=sum-of-sq, 2=param, 3=both
+        #   info // 10 % 10  -> 1 = problem not full rank at solution
+        convergence_status = out.info % 10
+        rank_deficient = (out.info // 10 % 10) == 1
+
+        if convergence_status in [1, 2, 3] and rank_deficient:
             warnings.warn(
-                "ODR fit is rank deficient. This may indicate a vanishing "
-                "chi-squared (n_obs == n_parms). Results may be unreliable.",
+                f"ODR fit is rank deficient (irank={out.irank}, inv_condnum={out.inv_condnum:.2e}). "
+                "This may indicate a vanishing chi-squared (n_obs == n_parms). "
+                "Results may be unreliable.",
                 RuntimeWarning
             )
         else:

setup.py

@@ -25,7 +25,7 @@ setup(name='pyerrors',
       license="MIT",
       packages=find_packages(),
       python_requires='>=3.10.0',
-      install_requires=['numpy>=2.0', 'autograd>=1.7.0', 'numdifftools>=0.9.41', 'matplotlib>=3.9', 'scipy>=1.13', 'iminuit>=2.28', 'h5py>=3.11', 'lxml>=5.0', 'python-rapidjson>=1.20', 'pandas>=2.2', 'odrpack>=0.4'],
+      install_requires=['numpy>=2.0', 'autograd>=1.7.0', 'numdifftools>=0.9.41', 'matplotlib>=3.9', 'scipy>=1.13', 'iminuit>=2.28', 'h5py>=3.11', 'lxml>=5.0', 'python-rapidjson>=1.20', 'pandas>=2.2', 'odrpack>=0.5'],
       extras_require={'test': ['pytest', 'pytest-cov', 'pytest-benchmark', 'hypothesis', 'nbmake', 'flake8']},
       classifiers=[
           'Development Status :: 5 - Production/Stable',