Fix SVG stroke-width import: style-parsed widths and element scale

[earlye]

Summary

• Bug 1: loadBoundingBoxAttributes was resetting mLineWidth to 1.0 whenever the direct stroke-width XML attribute was absent and the current value was < 1.0. This silently clobbered values already correctly parsed from the elements styleattribute (which has higher CSS priority than presentation attributes). Inkscape-exported SVGs nearly always putstroke-widthinstyle`, so this fired constantly.

• Bug 2: BoxSvgAttributes::apply was multiplying the stroke width by the elements own transform scale factor at import time, then the same scale was re-applied at render time via fScaledTransform(double-scaling). For a path withtransform="scale(0.26458333)" (Inkscapes px-to-mm factor), the combined effect was scale^2 = 0.07 instead of 0.26, making strokes ~4x too wide when both bugs are present.

• Also adds temporary debug logging under QT_LOGGING_RULES=friction.svg.import and a just run-debug-stroke-width target that filters to those lines for verification.

Test plan

• Import a character SVG from slime-at-school; check that stroke widths on scaled paths now visually match Inkscape at equivalent zoom
• Run just run-debug-stroke-width, import the same SVG, confirm rawWidth values match the SVG stroke-width values and strokeScale=1 (fixed) for all paths
• Verify paths with no stroke (stroke:none) are unaffected
• Verify paths with stroke-width as a direct XML attribute (not in style) are unaffected

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