[ENH] Implement dynamic docstring formula injection for distributions

[KaranSinghDev]

Reference Issues/PRs

#689 #698

What does this implement/fix? Explain your changes.

A robust mechanism to inject distribution-specific LaTeX formulas into the generic public methods of BaseDistribution (e.g., pdf, cdf, mean, var, energy).

Key things done:

1. Indentation-Aware Engine: Automatically matches base docstring indentation to ensure valid Sphinx rendering.
2. Inheritance Safety: Uses a factory wrapper with functools.wraps in init_subclass to preserve metadata and handle multi-level inheritance safely.
3. Demos: Fully implemented hooks for Normal, Rayleigh, Exponential, and Laplace.

Fallback (Weibull PDF)

Injected Math (Rayleigh PDF - custom)

Does your contribution introduce a new dependency? If yes, which one?

No

What should a reviewer concentrate their feedback on?

1.The robustness of the init_subclass implementation.
2. The indentation logic in _inject_formula_doc which was designed to fix the rendering failures discussed in #698.
3. The demonstration implementations in Normal, Rayleigh, Exponential, and Laplace.

Did you add any tests for the change?

Implemented a comprehensive suite in skpro/distributions/tests/test_docstring_injection.py verifying:
1.Injection in hooked classes.
2.Clean fallback (placeholder removal) in unhooked classes across all 12 methods.
3. Execution safety and metadata integrit

Any other comments?

I have implemented the hooks for 4 major distributions. If this approach is decent, I would be happy to extend the formulas to the rest of the distribution registry.
@fkiraly, please let me know if this mechanism meets the project's standards for the documentation pipeline.

P.S @fkiraly this could have been done earlier but I was submitting the abstract of my research project thus the delay.

PR checklist

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• The PR title starts with either [ENH], [MNT], [DOC], or [BUG]. [BUG] - bugfix, [MNT] - CI, test framework, [ENH] - adding or improving code, [DOC] - writing or improving documentation or docstrings.

For new estimators

• I've added the estimator to the API reference - in docs/source/api_reference/taskname.rst, follow the pattern.
• I've added one or more illustrative usage examples to the docstring, in a pydocstyle compliant Examples section.
• If the estimator relies on a soft dependency, I've set the python_dependencies tag and ensured
  dependency isolation, see the estimator dependencies guide.

[fkiraly]

Somehow your approach causes recursion in the pdf method. I suspect this might be due to how this interacts with _has_implementation_of?

[KaranSinghDev]

@fkiraly Thank you for the observation. I have checked it and I overrode _has_implementation_of in BaseDistribution to unwind the __wrapped__ chain. It now correctly identifies inherited methods even when wrapped for docstring injection.
I have verified locally with a targeted recursion test and the full Test All Distributions suite .