feat(python): expose qudit reference simulators

[qciaran]

Summary

• add thin PyO3 bindings for generalized qudit and dimension-fixed qutrit state-vector and density-matrix simulators
• expose operators, Kraus channels, instruments, measurements, reset/preparation, reduced states, diagnostics, and helper channels using ordinary Python sequences
• add pecos_rslib.simulators type stubs, high-level pecos.simulators re-exports, and user documentation
• add fixed-seed deterministic Python verification without a NumPy runtime dependency

Validation

• cargo check -p pecos-rslib
• cargo clippy -p pecos-rslib --all-targets -- -D warnings
• Ruff checks
• 7 focused Python tests pass
• high-level pecos.simulators import smoke test passes

Stacked on #588; retarget to dev after #588 merges.