Remove version pin from arviz dependency (#27)

Remove the  floor from the arviz dependency in pyproject.toml.
With no version floor, pip never upgrades an existing arviz install (any
version satisfies the constraint), so installing tidydraws cannot corrupt
the user's arviz/numpy/xarray environment.

This resolves the packaging concern raised in #26 (now closed): the
install-corruption problem only arises when the declared floor is above
what the user has installed. No floor means no upgrade.

The entire Bayesian audience already has arviz (PyMC depends on it), so
declaring arviz as a dependency is honest — the core extraction path
needs it to run. The no-arviz edge user (xarray + hand-built DataTree)
gets arviz pulled, which is expected and correct.

Closes #26. See #19 for the broader extraction-engine discussion.

Author: drbenvincent

pyproject.toml

@@ -29,7 +29,7 @@ classifiers = [
 requires-python = ">=3.12"
 dependencies = [
     "polars >=0.20",
-    "arviz>=0.12",
+    "arviz",
     "xarray",
     "numpy",
     "pyarrow>=24.0.0",