[BUG] GeneralizedPareto: false log_pdf exact tag, missing distr:paramtype, insufficient test params

[ANANYA542]

Describe the bug

GeneralizedPareto in skpro/distributions/gen_pareto.py has three related issues:

1. log_pdf falsely listed as capabilities:exact
   The _tags dictionary includes "log_pdf" in "capabilities:exact", but the class has no _log_pdf method. Since GeneralizedPareto extends BaseDistribution directly and not _ScipyAdapter, there is no adapter to provide it automatically. Every call to log_pdf() silently falls back to np.log(self.pdf(x)) in the base class and raises a warning — directly contradicting the "exact" tag.
2. Missing distr:paramtype tag
   GeneralizedPareto.get_class_tag("distr:paramtype") returns "general", falling back to the base class default. Every other scipy-backed parametric distribution in the library explicitly sets "distr:paramtype": "parametric".
3. Only 2 test parameter sets
   The standard across the library is 3 sets covering array case, index/columns case, and scalar case. GeneralizedPareto only has 2 and neither is a scalar case.

To Reproduce
import warnings
import pandas as pd
from skpro.distributions.gen_pareto import GeneralizedPareto
d = GeneralizedPareto(
xi=0.1, mu=0.0, sigma=1.0,
index=pd.Index([0]), columns=pd.Index(["y"])
)
x_df = pd.DataFrame({"y": [1.0]})
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter("always")
result = d.log_pdf(x_df)
if w:
print("Warning:", w[0].message)

print("log_pdf result:", result.iloc[0, 0])
print("_log_pdf in class:", "_log_pdf" in GeneralizedPareto.dict)
print("distr:paramtype:", GeneralizedPareto.get_class_tag("distr:paramtype"))

A screenshot of the reproduction output is attached below:

Expected behavior

1. log_pdf should not be listed under "capabilities:exact" unless _log_pdf is actually implemented
2. "distr:paramtype" should return "parametric" not "general"
3. There should be 3 test parameter sets consistent with library convention

Environment
OS: macOS
Python: 3.x
skpro: main branch (latest)

Additional context
All three issues live in skpro/distributions/gen_pareto.py. If confirmed, happy to open a PR fixing all three in the same file

[ANANYA542]

Hey @fkiraly — found these three issues while going through the distributions codebase. The log_pdf false tag is the most critical one since it silently returns numerically unstable results while claiming to be exact. Happy to open a PR fixing all three in the same file if this looks good to you

[JiwaniZakir]

Investigating this now, should have a patch shortly.