feat(stdlib): Tiled P0 — XML reader + base64 decode + gzip framing (#67)

The three parsing primitives the TMX path needs that were not already in
the tree (zlib inflate + the JSON reader already shipped):

- Xml.* — a minimal, deterministic pure-Ludic XML reader for the
  element/attribute/CDATA subset TMX/TSX/TX use, spliced on demand. Handles
  nested elements, single/double-quoted attributes, text + <![CDATA[…]]>,
  comments, the <?xml?> prolog and <!DOCTYPE>, the five predefined entities
  and numeric character references.
- Base64.* — standard base64 (RFC 4648) decode + a matching pure-Ludic
  encoder; the decoder ignores the whitespace Tiled wraps into <data>.
  Splicing Base64.* also pulls in inflate.ludic so a plain tool can run the
  full base64 -> zlib/gzip decode chain.
- z_gunzip — gzip framing (RFC 1952) over the existing DEFLATE inflater:
  skip the 10-byte header + optional fields, inflate the body, ignore the
  CRC32/ISIZE trailer.

Golden corpus vendored under assets/tiled-fixtures/ (mapeditor/tiled
examples, attributed, + hand-authored multi-encoding fixtures). New
example library/tiled_p0.ludic proves all three (21 assertions); docs
pages + inventory added so check-impl stays green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/language/xml/_section.md

@@ -0,0 +1,7 @@
+---
+id: xml
+title: Xml
+order: 40
+---
+
+A minimal, deterministic XML reader for the element/attribute/CDATA subset the native Tiled formats (TMX/TSX/TX) use. <a href="xml-parse"><code>Xml.parse</code></a> turns a document into an element tree; the accessors read a node's <a href="xml-tag"><code>tag</code></a>, <a href="xml-text"><code>text</code></a>, attributes (<a href="xml-attr"><code>Xml.attr</code></a>/<a href="xml-attr_int"><code>Xml.attr_int</code></a>/<a href="xml-has"><code>Xml.has</code></a>) and children (<a href="xml-child"><code>Xml.child</code></a>/<a href="xml-find"><code>Xml.find</code></a>/<a href="xml-count"><code>Xml.count</code></a>). It expands the five predefined entities and numeric character references, skips the <code>&lt;?xml?&gt;</code> prolog, comments and <code>&lt;!DOCTYPE&gt;</code>, and is best-effort rather than validating — the same contract as <a href="json"><code>Json</code></a>. Spliced on demand when a program mentions <code>Xml.*</code>.

docs/language/xml/xml-attr.md

@@ -0,0 +1,14 @@
+---
+id: xml-attr
+name: Xml.attr
+category: xml
+kind: namespace-method
+tokens: Xml.attr
+sig: Xml.attr(node, key: string) -> string
+tip: An attribute's value by name.
+order: 4
+ns: Xml
+member: attr
+---
+
+Returns the value of attribute <code>key</code> (entity-decoded), or <code>""</code> if the element has no such attribute. Use <a href="xml-has"><code>Xml.has</code></a> to distinguish an empty value from an absent one.

docs/language/xml/xml-attr_count.md

@@ -0,0 +1,14 @@
+---
+id: xml-attr_count
+name: Xml.attr_count
+category: xml
+kind: namespace-method
+tokens: Xml.attr_count
+sig: Xml.attr_count(node) -> int
+tip: How many attributes the element has.
+order: 7
+ns: Xml
+member: attr_count
+---
+
+Returns the number of attributes on <code>node</code>.

docs/language/xml/xml-attr_int.md

@@ -0,0 +1,14 @@
+---
+id: xml-attr_int
+name: Xml.attr_int
+category: xml
+kind: namespace-method
+tokens: Xml.attr_int
+sig: Xml.attr_int(node, key: string, dflt: int) -> int
+tip: An attribute parsed as an integer.
+order: 5
+ns: Xml
+member: attr_int
+---
+
+Returns attribute <code>key</code> parsed as a signed decimal integer, or <code>dflt</code> when the attribute is absent.

docs/language/xml/xml-child.md

@@ -0,0 +1,14 @@
+---
+id: xml-child
+name: Xml.child
+category: xml
+kind: namespace-method
+tokens: Xml.child
+sig: Xml.child(node, index: int) -> xml
+tip: A child element by index.
+order: 9
+ns: Xml
+member: child
+---
+
+Returns the child element at <code>index</code> in document order, or an empty node if the index is out of range.

docs/language/xml/xml-child_count.md

@@ -0,0 +1,14 @@
+---
+id: xml-child_count
+name: Xml.child_count
+category: xml
+kind: namespace-method
+tokens: Xml.child_count
+sig: Xml.child_count(node) -> int
+tip: How many child elements.
+order: 8
+ns: Xml
+member: child_count
+---
+
+Returns the number of direct child elements of <code>node</code> (text and comments are not children).

docs/language/xml/xml-count.md

@@ -0,0 +1,14 @@
+---
+id: xml-count
+name: Xml.count
+category: xml
+kind: namespace-method
+tokens: Xml.count
+sig: Xml.count(node, tag: string) -> int
+tip: How many children have a given tag.
+order: 11
+ns: Xml
+member: count
+---
+
+Returns how many direct children of <code>node</code> are named <code>tag</code> — e.g. the number of <code>&lt;layer&gt;</code> elements in a map.

docs/language/xml/xml-find.md

@@ -0,0 +1,14 @@
+---
+id: xml-find
+name: Xml.find
+category: xml
+kind: namespace-method
+tokens: Xml.find
+sig: Xml.find(node, tag: string) -> xml
+tip: The first child with a given tag.
+order: 10
+ns: Xml
+member: find
+---
+
+Returns the first direct child of <code>node</code> whose tag is <code>tag</code>, or an empty node if there is none.

docs/language/xml/xml-has.md

@@ -0,0 +1,14 @@
+---
+id: xml-has
+name: Xml.has
+category: xml
+kind: namespace-method
+tokens: Xml.has
+sig: Xml.has(node, key: string) -> int
+tip: Whether an attribute is present.
+order: 6
+ns: Xml
+member: has
+---
+
+Returns <code>1</code> if <code>node</code> carries attribute <code>key</code>, else <code>0</code>.

docs/language/xml/xml-parse.md

@@ -0,0 +1,14 @@
+---
+id: xml-parse
+name: Xml.parse
+category: xml
+kind: namespace-method
+tokens: Xml.parse
+sig: Xml.parse(text: string) -> xml
+tip: Parse XML text into an element tree.
+order: 1
+ns: Xml
+member: parse
+---
+
+Parses an XML document and returns its root element (or an empty node if there is none). Handles nested elements, single- and double-quoted attributes, text/<code>&lt;![CDATA[…]]&gt;</code> content, comments, the <code>&lt;?xml?&gt;</code> prolog and <code>&lt;!DOCTYPE&gt;</code>. Best-effort, not validating.

docs/language/xml/xml-tag.md

@@ -0,0 +1,14 @@
+---
+id: xml-tag
+name: Xml.tag
+category: xml
+kind: namespace-method
+tokens: Xml.tag
+sig: Xml.tag(node) -> string
+tip: The element's tag name.
+order: 2
+ns: Xml
+member: tag
+---
+
+Returns the element name of <code>node</code> (e.g. <code>tileset</code>), or <code>""</code> for the empty node.

docs/language/xml/xml-text.md

@@ -0,0 +1,14 @@
+---
+id: xml-text
+name: Xml.text
+category: xml
+kind: namespace-method
+tokens: Xml.text
+sig: Xml.text(node) -> string
+tip: The element's character data.
+order: 3
+ns: Xml
+member: text
+---
+
+Returns the concatenated character data of <code>node</code> — the CSV inside a <code>&lt;data encoding="csv"&gt;</code> element, or a <code>&lt;property&gt;</code> value, lands here (entity-decoded).