[BUG] RFD3 symmetry fails for odd dihedral groups D3/D5

[runrah]

Unconditional symmetric generation in RFD3 appears to fail for odd dihedral symmetry groups. In rc-foundry 0.1.12, C3, D2, and D4 run successfully, but D3 and D5 fail during ConditionalRoute -> AddSymmetryFeats with a tensor size mismatch.

I ran the following command:

rfd3 design \
    inputs=test.yaml \
    out_dir=test \
    ckpt_path=/path/to/latest.ckpt \
    n_batches=1 \
    diffusion_batch_size=1 \
    low_memory_mode=True \
    inference_sampler.kind=symmetry

with the following test.yaml file:

D3_test:
  length: 100
  is_non_loopy: true
  symmetry:
    id: "D3"

This fails with the following error:

RuntimeError: Transforms failed at stage `ConditionalRoute -> AddSymmetryFeats`:
The size of tensor a (6) must match the size of tensor b (4) at non-singleton dimension 0

The same setup works when changing the symmetry ID to C3, D2, or D4, but fails for D3 and D5.