share='labels' is disabled after formatting individual subplots in UltraPlot 2.7.0 #833

Question

Has the behavior of share='labels' with individual ax.format() calls changed between UltraPlot 2.5.0 and 2.7.0?

My existing multi-panel figure showed shared x/y labels with 2.5.0. After upgrading to 2.7.0, each subplot shows its own labels. I can reproduce the sharing-state change without my project code or data.

Minimal reproducible example

import ultraplot as uplt

fig, axs = uplt.subplots(
    [[1, 1], [2, 3], [4, 5]],
    share="labels",
)

print("Initially:", fig.get_axis_sharing())

axs[0].plot([0, 1], [1, 2])
axs[0].format(title="Total", ylabel="Value")

for i, ax in enumerate(axs[1:], 1):
    ax.plot([0, 1], [i, i + 1])
    ax.format(title=f"Panel {i}", xlabel="Year", ylabel="Value")

print("After formatting:", fig.get_axis_sharing())
fig.show()

Observed with 2.7.0

Immediately after subplots(), both x and y have level: 1 and labels: True. After the individual format() calls, both become level: 0 and labels: False; the spanning labels are disabled as well.

Expected behavior

I expected the identical axis-title strings to remain shared, as they appeared in my figure made with 2.5.0. Is this an intentional change? If so, what is the recommended migration for figures that set titles and other formatting on each subplot?

Formatting the common labels at figure/grid level appears to work around the problem, but I would like to understand whether the original usage should still be supported.

Environment

• UltraPlot: 2.7.0
• Python: 3.12.11
• Matplotlib: 3.10.5
• OS: Windows

I have not rerun this exact minimal example under 2.5.0; the 2.5.0 comparison is based on my previously generated figure.