Add Core zFPKM Tests

[JoshLoecker]

This pull request adds unit tests to:

• density calculation
• peak finding
• interpolation

[Copilot]

Pull Request Overview

This PR modernizes the codebase by replacing NumPy-specific float types (like np.float64, np.float32, np.int8) with Python's built-in float and int types. Key changes include:

• Replacing NumPy-specific dtype specifications with Python built-ins
• Adding new utility functions for kernel density estimation (density.py, approx.py, peak_finder.py)
• Updating type annotations to use float and int instead of NumPy types
• Adding a type checker configuration file (ty.toml)
• Improving gene data handling and conversions
• Various code quality improvements and refactoring

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
ty.toml	Adds type checker configuration
tests/unit/*.py	New comprehensive test files for density, approx, and peak_finder modules
tests/unit/test_*.py	Updates dtype specifications from np.float32/int8 to built-in float/int
main/como/utils.py	Adds itertools import, improves type annotations and error handling
main/como/stats/*.py	Replaces np.float64 with float in type annotations
main/como/rnaseq_*.py	Major refactoring: replaces scipy/sklearn with custom R-compatible implementations
main/como/data_types.py	Updates Enum values to lowercase, adds defaults to PeakIdentificationParameters
main/como/density.py	New module implementing R's density function
main/como/approx.py	New module implementing R's approx function
main/como/peak_finder.py	New module implementing R's findpeaks function

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