PR summary

closes#30472

This PR fixes a colorbar alignment issue when using compressed layout mode
with suptitle. In compressed layout, whenapply_aspect() is called on
axes (triggered by the presence of a suptitle), colorbars were not
properly aligning with their parent axes because they were being sized
based on the pre-aspect-adjustment dimensions.

Why is this change necessary?
When usinglayout='compressed' with a suptitle, the axes undergo aspect
ratio adjustments that change their visual height. Colorbars attached to
these axes were not accounting for this adjustment, resulting in
misaligned colorbars that didn't match their parent axes' vertical extent.

What problem does it solve?
Colorbars now properly align with their parent axes in compressed layout
mode, maintaining the same height and vertical position even when the
parent axes have been resized by aspect ratio constraints.

What is the reasoning for this implementation?
The fix passes acompress flag through the repositioning chain and, when
in compressed mode with single-parent vertical colorbars, uses the actual
post-aspect-adjustment position of the parent axis to calculate the
colorbar's bounding box. This ensures the colorbar dimensions match the
visually rendered parent axes rather than the pre-adjustment layout grid
dimensions.

Example:

importnumpyasnpimportmatplotlib.pyplotaspltarr=np.arange(100).reshape((10,10))fig,axs=plt.subplots(ncols=2,figsize=(4,2),layout='compressed')axs[0].imshow(arr)axs[1].imshow(arr)plt.colorbar(axs[0].images[0],ax=axs[0])plt.colorbar(axs[1].images[0],ax=axs[1])fig.suptitle('Title')plt.show()

PR checklist

• "closes #0000" is in the body of the PR description to link the related
  issue
• new and changed code is tested
• [N/A] Plotting related features are demonstrated in an example
• [N/A] New Features and API Changes are noted with a directive and
  release note
• [N/A] Documentation complies with general and docstring guidelines