Fix createTextPath CJK glyph extraction for mixed CJK/English text

[Copilot]

The createTextPath function in web_content_renderer.cpp was failing to correctly extract glyph paths from CJK (Chinese, Japanese, Korean) characters when processing mixed CJK/English text. This prevented CSS background-clip: text effects from working properly with multilingual content.

Problem

The original implementation used a single font for the entire text string and manually calculated glyph positions:

// Old approach - single font selection
sk_sp<SkTypeface> typeface = fontCollection->findTypefaces(...)[0];
SkFont font(typeface, fontSize);
font.textToGlyphs(textContent.c_str(), textContent.size(), ...);
// Manual positioning and glyph path extraction

This approach failed because:

• No single font provides high-quality glyphs for both English and CJK scripts
• Manual glyph positioning didn't account for complex script requirements
• When the selected font lacked CJK glyphs, font.getPath() would fail and CJK characters were silently skipped

Solution

Replaced the single-font approach with Skia's paragraph visitor pattern, which leverages the paragraph system's proper font resolution:

// New approach - use paragraph's resolved fonts
paragraph->visit([&](int lineNumber, const Paragraph::VisitorInfo* info) {
  for (int i = 0; i < info->count; ++i) {
    SkPath glyphPath;
    if (info->font.getPath(info->glyphs[i], &glyphPath)) {
      // Uses the correct font for each glyph
      // Uses paragraph's calculated positions
    }
  }
});

Impact

This fix enables background-clip: text CSS effects to work correctly with:

• Pure CJK text: "你好世界"
• Mixed scripts: "Hello 你好 World 世界"
• Complex multilingual content: "News 新闻 ニュース 뉴스 📰"

Example CSS that now works with CJK text:

.gradient-text {
  background: linear-gradient(45deg, #ff6b6b, #4ecdc4);
  background-clip: text;
  -webkit-background-clip: text;
  color: transparent;
}

The change is minimal (28 additions, 70 deletions) and leverages existing Skia infrastructure rather than maintaining custom text layout logic.

Fixes #150.

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