[bug] `pyro.render_model` omits edges

[YardenRachamim]

Issue Description

context: linear ordinal regression model using OrderedLogistic distribution
problem: pyro.render_model fails to draw edges when a child pyro.sample site
receives a tensor produced by either

• a pyro.deterministic site, or
• a pyro.sample site wrapped in a Delta transform (e.g. to enforce ordering).

That makes the rendered DAG incorrect parents are silently hidden.
I think the inference worked fine but can't tell for sure.

Environment

• OS: Ununto
• python version: 3.10.
• PyTorch version: 2.6.0+cpu
• Pyro version: 1.9.1

Code Snippet

def ordinal_regression_model(X, y=None):
    D = X.size(-1)
    num_categories = 3

    cutpoints = pyro.param(
        "cutpoints",
        torch.linspace(-1., 1., num_categories - 1, dtype=X.dtype, device=X.device),
        constraint=constraints.ordered_vector
    )
#     cutpoints = pyro.sample(
#         "cutpoints",
#         dist.TransformedDistribution(                     # base → transform → ordered
#             dist.Normal(
#                 torch.zeros(num_categories - 1, device=X.device, dtype=X.dtype),
#                 torch.ones(num_categories - 1, device=X.device, dtype=X.dtype),
#             ).to_event(1),                                # joint prior over the vector
#             OrderedTransform(),                # enforces monotonicity
#         ),
#     )
    
    loc = torch.zeros(D, dtype=X.dtype, device=X.device)
    scale = torch.ones_like(loc) * 5
    beta = pyro.sample("beta", dist.Normal(loc=loc, scale=scale).to_event(1))  # D
#     eta = pyro.deterministic("eta", X.float() @ beta.float())
    eta = pyro.sample(          # now a sample site
        "eta",
        dist.Delta((X.float() @ beta.float())).to_event(1)
    )
    with pyro.plate("data", X.size(0)):
        pyro.sample(
            "obs",
            dist.OrderedLogistic(eta, cutpoints),  # OrderedLogistic does its own broadcast
            obs=y
        )

pyro.render_model(
    ordinal_regression_model,
    model_args=(batch[0], batch[1]),
    render_params=True,
    render_distributions=True,
    render_deterministic=True
)

Expected Behaviour

Graph should explicitly show the dependency chain: beta → eta → obs
including the plate context and cutpoints as parameters. Any tensor passed as a parameter to a sample site's distribution, regardless of being computed via pyro.deterministic or via a Delta-transformed sample, should be considered as a parent when computing edges.

Note: Attempted workarounds such as:

• Wrapping the tensor explicitly with pyro.deterministic.
• Using a pyro.sample site with a Delta distribution.

All attempts listed above still failed to display the missing edge.

Actual Behaviour