* fix(html): percent-escape non-ASCII characters in URI-valued attributes
XSLT 1.0 16.2 / HTML 4.01 B.2.1: the html output method percent-escapes
non-ASCII and control characters in attributes of type %URI (href, src, cite,
action, and the rest), writing each as the uppercase hex of its UTF-8 bytes,
while keeping " and & as entities. Other attributes are unaffected. The
serializer left such characters unescaped. Grounded in the libxml2
htmlSerializeUri study; reimplemented in pure Swift, no Foundation.
Closes Apache Xalan conformance case output32.
* docs(html): disclose URI-attribute escaping round-trip normalization
Address the URI-escaping critics: the html serializer follows libxml2's HTML
output model where URI-valued attributes are always percent-escaped, so a
parse-then-serialize round-trip normalizes a space or non-ASCII byte to %HH.
Document that this is idempotent (a literal % is left as is) and that every
space is escaped (leading ones included, where libxml2 skips them). Add an
idempotency test.
basefont and isindex join the void-element set, and the html output
method leaves an ampersand unescaped when a brace follows (the
&{...} attribute convention of XSLT 16.2). Xalan baseline 134 -> 131
(output 20 -> 17).
Same-name xsl:attribute-set declarations merge as ordered definitions
per 7.1.4, each expanding its used sets before its own attributes with
later definitions winning; xsl:copy carries the source element's
in-scope namespace nodes per 7.5; the namespace fixup lets a carried
attribute prefix shadow an inherited binding unless the element's own
name relies on it; the html method minimizes boolean attributes whose
value repeats their name; and external DTDs and entities in the
stylesheet or source resolve through the transform's document loader.
Four unit tests pin the behaviors. Xalan baseline 174 -> 159
(attribset 13 -> 4, copy 12 -> 7).
Add the PureXML.HTML namespace: a lenient tokenizer for tag-soup input
(case-insensitive tags; quoted, unquoted, and boolean attributes; comments;
doctype; character references), a tree builder handling void elements,
optional end tags (li, p, table rows and cells), raw-text elements (script,
style), and unmatched end tags, and a serializer that writes void elements
unclosed and raw-text content unescaped.
Closes#36Closes#37Closes#38Closes#39Closes#20
