Diagnostics pane graphs getting bigger and bigger

[ap0int3d]

Describe the bug
The Diagnostics pane graphs get bigger and bigger each time you go back and forth between the Workspaces tab and any other tab (File Manager, Hosts or Commands)

To Reproduce
Steps to reproduce the behavior:

1. Open an SSH session to an host
2. Open the Diagnostics pane for this hosts
3. Go to File Manager or Hosts or Commands tab
4. Go back to Workspaces tab
5. Repeat step 3 and 4 several times
6. See graphs getting bigger each time

Expected behavior
Graph size should not change.

Screenshots
Initial size:

After some back and forth:

Desktop (please complete the following information):

• OS: Windows 11
• Browser: Firefox
• Version: 140.14.0esr

[bifrost0x]

Fixed in PR #191. Diagnostics canvases now skip redraws while their layout is hidden, keep CSS in control of their logical dimensions, and redraw after returning to Workspaces. The PR also adds unit coverage for hidden high-DPI canvases and a browser regression that repeats the Diagnostics/File Manager navigation cycle four times without any size change.