Fix gradient coordinate percentage parsing

[KuroiDOC]

Problem

linearGradient and radialGradient elements frequently use percentage values for their geometry attributes (x1, y1, x2, y2, cx, cy, r, fx, fy, fr). Per SVG 1.1 §13.2.2, with the default gradientUnits="objectBoundingBox", 50% is equivalent to
the fraction 0.5.

SwiftDraw's scanCoordinate only recognised px/in/cm/mm/pt/pc as unit suffixes. The % was left unconsumed and the bare number was returned — so x1="3.309%" became 3.309 instead of 0.03309, placing the gradient axis far outside the bounding box
and rendering the wrong colours.

Solution

Added scanCoordinateOrPercentage() to XMLParser.Scanner — identical to scanCoordinate but consumes a trailing % and divides the value by 100. The new method is wired through AttributeValueParser and used exclusively in the linear and radial
gradient parsers.

Generic coordinate parsing is intentionally left unchanged: % on non-gradient attributes (e.g. ) is viewport-relative and requires resolution context that doesn't exist in the parser layer yet.

Testing

• New unit tests covering percentage x1/y1/x2/y2 parsing in ParserXMLLinearGradientTests and percentage cx/cy/r/fx/fy in ParserXMLRadialGradientTests
• Existing non-percentage gradient tests confirm no regression

Examples

Demo SVG:

Safari rendering	Previous rendering	Fixed

[codecov]

Codecov Report

❌ Patch coverage is 96.87500% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.61%. Comparing base (3981bb8) to head (f8476b9).

Files with missing lines	Patch %	Lines
DOM/Sources/Parser.XML.swift	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #127      +/-   ##
==========================================
+ Coverage   89.58%   89.61%   +0.02%     
==========================================
  Files         161      161              
  Lines       12597    12651      +54     
==========================================
+ Hits        11285    11337      +52     
- Misses       1312     1314       +2     

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