Stroke Alpha can render tool outlines/crosshairs invesible
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#### Summary:
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The outline of tool icons (on canvas) and crosshairs use the alpha value of the stroke. This makes them invisble if it is set too low. Regression from 1.3.2. No duplicates with ~regression + storke/outline/alpha
#### Steps to reproduce:
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- open Inkscape
- Choose the rectangle tool
- Make sure 'Last used style' is on (the default)
- set alpha of stroke to 0
- create a rectangle
#### What happened?
No cross-hair; similarly, no outline for the bezier tool
#### What should have happened?
Crosshar/outline are visible
Sample attachments:
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#### Version info
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Inkscape 1.4.1 (7c588ab6e4, 2025-04-03)
Compile (Run)
GLib version: 2.82.2
GTK version: 3.24.43 (3.24.43)
glibmm version: 2.66.7
gtkmm version: 3.24.9
libxml2 version: 2.12.8
libxslt version: 1.1.42
Cairo version: 1.18.2 (1.18.2)
Pango version: 1.54.0 (1.54.0)
HarfBuzz version: 9.0.0 (9.0.0)
OS version: Fedora Linux 41 (Workstation Edition)
```
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issue