[Bug] Heatmap CLI fails on time‑stacked NetCDFs (3D arrays)

[jphpme]

Title: visualize heatmap fails on time‑stacked NetCDFs (3D arrays) — Invalid shape (48, 721, 1440)

Description:
zyra visualize heatmap fails when the NetCDF variable contains a time dimension (3D array). The CLI passes the full (time, lat, lon) array into matplotlib.imshow, which raises a shape error.

Exact error

Warning: Input CRS unknown; assuming EPSG:4326.
Traceback (most recent call last):
File "/opt/venv/bin/zyra", line 8, in
sys.exit(main())
File "/opt/venv/lib/python3.10/site-packages/zyra/cli.py", line 1164, in main
return args.func(args)
File "/opt/venv/lib/python3.10/site-packages/zyra/visualization/cli_heatmap.py", line 84, in handle_heatmap
mgr.render(
File "/opt/venv/lib/python3.10/site-packages/zyra/visualization/heatmap_manager.py", line 165, in render
im = ax.imshow(
File "/opt/venv/lib/python3.10/site-packages/cartopy/mpl/geoaxes.py", line 291, in wrapper
return func(self, *args, **kwargs)
File "/opt/venv/lib/python3.10/site-packages/cartopy/mpl/geoaxes.py", line 1275, in imshow
result = super().imshow(img, *args, **kwargs)
File "/opt/venv/lib/python3.10/site-packages/matplotlib/init.py", line 1524, in inner
return func(
File "/opt/venv/lib/python3.10/site-packages/matplotlib/axes/_axes.py", line 5982, in imshow
im.set_data(X)
File "/opt/venv/lib/python3.10/site-packages/matplotlib/image.py", line 685, in set_data
self._A = self._normalize_image_array(A)
File "/opt/venv/lib/python3.10/site-packages/matplotlib/image.py", line 653, in _normalize_image_array
raise TypeError(f"Invalid shape {A.shape} for image data")
TypeError: Invalid shape (48, 721, 1440) for image data
Dataset context
ERA5 NetCDF with variables:

['number', 'valid_time', 'latitude', 'longitude', 'expver', 't2m']

Expected behavior
If a time dimension exists and no explicit index is provided, render one frame per timestep (output directory), or
Allow a --time-index / --time flag for a single timestep, and error clearly if not provided.
Also consider handling extra dims like expver/number by defaulting to the first slice or supporting a selector.

Actual behavior
Zyra tries to render the full 3D array with imshow, causing a shape error.

Environment

Zyra CLI invoked inside Docker (Python 3.10)
Cartopy + Matplotlib
NetCDF input with time dimension (ERA5)