CI Optimization and Symmetry Loss

**Is your feature request related to a problem? Please describe.**
I'm working on benzene and optimizing CI coefficients from a CAS(6,6) calculation. Before optimization, I had several degenerate CSF coefficients due to D6h symmetry. However, after optimization, these coefficients become unequal, indicating that the procedure breaks symmetry.

**Describe the solution you'd like**
An option to constrain the CI coefficient optimization to preserve degeneracies, especially in symmetric systems. This would help maintain wavefunction symmetry and lead to more consistent and physically meaningful results.

**Describe alternatives you've considered**
One attempted workaround involved combining degenerate CSFs into a single CSF with multiple determinants. However, this manual modification led to noticeably different total energies and degraded the performance of cusp corrections, indicating that it is not a reliable solution.

Unmodified xml before optimization:
```






```
Unmodified xml after optimization:
```






```

Modified xml:
```




```
This modification was applied to all degenerate CSFs, though only the first two are shown here for readability

**Additional context**
Example energies at the cusp correction level:

- GAMESS reference: −230.8620665149
- QMC with unmodified XML: −230.847820 ± 0.014805
- QMC with modified XML (merged CSFs): −230.722973 ± 0.014256