Add basis

[johannes-moegerle]

merge after #16

preliminary work to properly add mqdt to rydstate

[Copilot]

Pull request overview

This PR adds a new basis module to rydstate that provides basis set functionality for SQDT (Semi-classical Quantum Defect Theory) Rydberg states, and refactors the angular module to use type guard functions for better type safety.

• Introduces BasisBase abstract class and concrete implementations BasisSQDTAlkali and BasisSQDTAlkalineLS for generating basis sets of Rydberg states
• Refactors angular momentum type checking from get_args() calls to dedicated type guard functions (is_angular_momentum_quantum_number, is_angular_operator_type)
• Enhances AngularKetBase with new calc_exp_qn and calc_std_qn methods for calculating quantum number expectation values and standard deviations

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/rydstate/basis/basis_base.py	Implements abstract base class for basis sets with methods for filtering states, calculating overlaps, and computing matrix elements
src/rydstate/basis/basis_sqdt.py	Provides concrete basis implementations for alkali and alkaline earth SQDT states with quantum number enumeration
src/rydstate/basis/__init__.py	Exports the two SQDT basis classes
src/rydstate/angular/angular_matrix_element.py	Adds type guard functions to replace runtime get_args() checks
src/rydstate/angular/angular_ket.py	Refactors to use type guards and adds quantum number calculation methods
src/rydstate/angular/angular_state.py	Updates imports to use type guards and changes parameter types from list to Sequence for more flexibility
src/rydstate/__init__.py	Exports the new basis classes from the main module

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