pymat.vis.client() (module function) vs .client (Vis property) — same concept, two spellings

[gerchowl]

Tier 3 — documentation clarity

Two callables, one concept ("get the shared `MatVisClient` singleton"):

from pymat import vis
c = vis.client()             # module-level function in pymat.vis.__init__

c = material.vis.client      # property on Vis — no parens

A brain-typo apart. The current docstrings don't cross-reference, so a
user who learns one won't immediately discover the other.

Fix

Add a side-by-side callout in both docstrings:

In `pymat/vis/init.py` `client()`:

Note: if you already have a Material, `material.vis.client` is the
same singleton without the parens.

In `pymat/vis/_model.py` `Vis.client` property:

Note: if you don't have a Material yet (tier enumeration, cache
management), `pymat.vis.client()` is the module-level entry point.

No code change

Naming stays the same — both spellings earn their keep:

• Module function is called before a material is picked.
• Instance property is called in material-keyed contexts.

The duplication is the feature; the docs should acknowledge it
explicitly.