Remove upstream-project references from source comments

The vendored CSS engine and the Html-layer files derived from the same lineage
carried doc comments naming the upstream project and its file paths. Provenance
belongs in the commit history and the PR description, not in the source, so the
comments now describe what the code does rather than where it came from.

No functional change. The one remaining mention is the vendor-prefixed property
name `-peachpdf-pdf-tag-type` itself, which is a CSS identifier rather than a
comment; it is inert here (nothing consumes tagged-PDF output) and renaming a
vendor prefix would diverge from the engine it is synced against.

Author: jhaygood86

Source/HtmlRenderer/Core/CssData.cs

@@ -26,8 +26,8 @@ namespace TheArtOfDev.HtmlRenderer.Core
     /// specificity-ordered selector matching against the box tree.<br/>
     /// </summary>
     /// <remarks>
-    /// Ported from PeachPDF's Html/Core/CssData.cs (itself a fork of Tyler Brinks' ExCSS), adapted to
-    /// HTML-Renderer's CssBox/HtmlTag shape. One deliberate omission from the source: the
+    /// Derived from the same ExCSS lineage as the vendored CSS-OM (originally Tyler Brinks' ExCSS),
+    /// adapted to HTML-Renderer's CssBox/HtmlTag shape. One deliberate omission from the source: the
     /// <c>::marker</c> pseudo-element box-synthesis path is removed - <c>::before</c>/<c>::after</c>
     /// synthesis is kept, but this codebase has no <c>CssBox.IsMarkerPseudoElement</c> concept and no
     /// consumer for it (list markers are painted procedurally, not via a synthesized box).

Source/HtmlRenderer/Core/CssEngine/BackgroundPositionGrammar.cs

@@ -6,7 +6,7 @@ namespace TheArtOfDev.HtmlRenderer.Core.CssEngine
     /// Shared grammar for the CSS <c>background-position</c> value (the 1/2/3/4-token forms,
     /// including the edge-relative offset syntax, e.g. "right 20px bottom 10px"). Used by both
     /// <see cref="Converters.PointConverter"/> (CSS-OM grammar validation/serialization) and
-    /// PeachPDF.Html.Core.Utils.BackgroundLayerResolver (render-time pixel-offset arithmetic) so
+    /// the render-time background-layer resolution (pixel-offset arithmetic) so
     /// there is one parser for this grammar, not two independent re-implementations - mirroring how
     /// CalcParser is shared between CalcValueConverter and CssValueParser rather than re-parsed twice.
     /// </summary>

Source/HtmlRenderer/Core/CssEngine/BackgroundSizeGrammar.cs

@@ -6,7 +6,7 @@ namespace TheArtOfDev.HtmlRenderer.Core.CssEngine
     /// Shared grammar for the CSS <c>background-size</c> value (<c>auto</c>, <c>cover</c>,
     /// <c>contain</c>, or a 1-2 token length/percentage/auto form). Used by both
     /// <see cref="Converters.BackgroundSizeConverter"/> (CSS-OM grammar validation/serialization)
-    /// and PeachPDF.Html.Core.Utils.BackgroundLayerResolver (render-time size resolution), so there
+    /// and the render-time background-layer resolution (size resolution), so there
     /// is one parser for this grammar, not two.
     /// </summary>
     internal static class BackgroundSizeGrammar

Source/HtmlRenderer/Core/CssEngine/Calc/CalcEvaluator.cs

@@ -34,7 +34,7 @@ public CalcContext(double hundredPercent, double emFactor, double remFactor, boo
 
     /// <summary>
     /// Evaluates a validated calc-family AST to a pixel-space number. This is the one place calc()
-    /// numbers actually get computed — called only from Layer B (<see cref="PeachPDF.Html.Core.Parse.CssValueParser.ParseLength(string, double, double, double, string, bool, bool)"/>),
+    /// numbers actually get computed — called only from Layer B (<c>CssValueParser.ParseLength</c>),
     /// since only layout has the <see cref="CalcContext"/> a percentage/em/rem leaf needs to resolve.
     /// Reuses <see cref="Length.ToPixels"/> for every leaf, so no unit-conversion arithmetic is duplicated
     /// here. A null result signals a divide-by-zero; per the type-checker's rules every legal divisor is

Source/HtmlRenderer/Core/CssEngine/Enumerations/PdfTagType.cs

@@ -1,7 +1,7 @@
 namespace TheArtOfDev.HtmlRenderer.Core.CssEngine
 {
     /// <summary>
-    /// Values for the PeachPDF-specific <c>-peachpdf-pdf-tag-type</c> property, which controls
+    /// Values for the vendor-prefixed <c>-peachpdf-pdf-tag-type</c> property, which controls
     /// the PDF structure (tag) type an element maps to when tagged PDF output is enabled.
     /// </summary>
     internal enum PdfTagType

Source/HtmlRenderer/Core/CssEngine/Model/Converters.cs

@@ -500,7 +500,7 @@ public static readonly IValueConverter
 
         public static readonly IValueConverter MultipleShadowConverter = ShadowConverter.FromList().OrNone();
 
-        // The image functions PeachPDF validates but does not render (CSS Images 4). Composed into
+        // The image functions the engine validates but the renderer does not paint (CSS Images 4). Composed into
         // ImageSourceConverter so every <image> property (background-image, list-style-image, cursor,
         // content, and @property syntax:"<image>") accepts them syntactically; the render path
         // (CssValueParser.ParseImage → CssImagePainter) still handles only url()/gradients, so they paint

Source/HtmlRenderer/Core/CssEngine/ValueConverters/ExtendedImageConverters.cs

@@ -7,7 +7,7 @@ namespace TheArtOfDev.HtmlRenderer.Core.CssEngine
 
     /// <summary>
     /// A validated-but-not-rendered image function (<c>image-set()</c>/<c>cross-fade()</c>/<c>element()</c>,
-    /// CSS Images 4 §2/§3). PeachPDF accepts these as syntactically-valid <c>&lt;image&gt;</c> values (so a
+    /// CSS Images 4 §2/§3). The engine accepts these as syntactically-valid <c>&lt;image&gt;</c> values (so a
     /// property or <c>@property</c> registration using one is valid, per spec) but paints nothing for them —
     /// the render path (<c>CssValueParser.ParseImage</c> → <c>CssImagePainter</c>) only handles url()/gradients.
     /// This value carries the original tokens for serialization only.

Source/HtmlRenderer/Core/Dom/CssContentEngine.cs

@@ -23,7 +23,7 @@ namespace TheArtOfDev.HtmlRenderer.Core.Dom
     /// Resolves a synthesized <c>::before</c>/<c>::after</c> pseudo-element box's <see cref="CssBox.Content"/>
     /// value into literal text, so it renders through the box's normal <see cref="CssBox.Text"/>/
     /// <see cref="CssBox.ParseToWords"/> machinery like any other text box.<br/>
-    /// Deliberately a small, self-contained subset of PeachPDF's CssContentEngine: literal strings,
+    /// Deliberately a small, self-contained subset of the full content grammar: literal strings,
     /// <c>attr()</c>, and the four quote keywords are supported; <c>counter()</c>/<c>counters()</c>/
     /// <c>string()</c>/<c>content()</c> are not (CSS counters and named strings remain out of scope
     /// for this backport - an unrecognized component is simply skipped, the same graceful-ignore

Source/HtmlRenderer/Core/Entities/CssImage.cs

@@ -2,7 +2,7 @@ namespace TheArtOfDev.HtmlRenderer.Core.Entities
 {
     /// <summary>
     /// The parsed form of a single <c>background-image</c> value: either a <c>url()</c> reference or a
-    /// gradient function. Unlike PeachPDF's <c>CssImage</c> (which this is a trimmed-down port of, same
+    /// gradient function. Unlike the fuller model this is trimmed down from (same
     /// name for an easy diff), <c>background-image</c> here is a single value, not a comma-separated
     /// layered list - this project only backports enough to replace the old non-standard
     /// "background-gradient" property.

Source/HtmlRenderer/Core/Entities/ParsedLinearGradient.cs

@@ -5,7 +5,7 @@ namespace TheArtOfDev.HtmlRenderer.Core.Entities
 {
     /// <summary>
     /// A fully parsed <c>linear-gradient()</c>/<c>repeating-linear-gradient()</c> value - the angle and
-    /// raw (not yet position-resolved) color stop list. Ported from PeachPDF's
+    /// raw (not yet position-resolved) color stop list. Derived from
     /// Html/Core/Entities/ParsedLinearGradient.cs, minus CSS Color 4 interpolation-color-space support
     /// (ColorSpace/HueMethod) - gradients always interpolate in sRGB here.
     /// </summary>