Fix patch_to to handle Enum and non-type iterables correctly

[ncoop57]

Problem

patch_to uses tuplify(cls) to iterate over the target class(es), but tuplify iterates over Enum members (and other iterables) rather than treating them as a single class, causing unexpected behaviour when patching Enum subclasses.

Fix

Check if cls is a plain type first and wrap it in a tuple directly, falling back to tuplify only for sequences of classes. This ensures Enum classes (and any other iterable types) are treated as a single patch target.

Also fixes an unrelated CI failure: matplotlib 3.11 detaches a figure's canvas on plt.close, breaking test_fig_exists when run via nbdev's inline backend. It now re-attaches an Agg canvas if needed.

Changes

• fastcore/basics.py: Replace bare tuplify(cls) with (cls,) if isinstance(cls, type) else tuplify(cls) in patch_to
• fastcore/test.py / nbs/00_test.ipynb: Make test_fig_exists re-attach a FigureCanvasAgg when the figure's canvas has been detached (matplotlib >= 3.11)

[jph00]

Thank you :)