Duckle v0.0.9

Engine: src.soap + XML response support in src.rest

Adds RestResponseFormat::Xml to RestSourceSpec so any REST request can
parse an XML body via the same element-path walker src.xml uses. The
walker is extracted into a free fn (walk_xml_to_rows) shared between
src.xml and the new REST/SOAP path; src.xml's own behavior is unchanged.

src.soap is a thin alias: matches!() in the planner adds defaults of
method=POST, Content-Type text/xml; charset=utf-8, responseFormat=xml,
plus an optional SOAPAction header from the soapAction prop. The user
supplies the envelope as `body` and the row_path as the element walk
into the response (e.g. Envelope/Body/GetUsersResponse/Users/User).

The XML walker now matches local-name when comparing row_path segments
to element names, so `Envelope/Body/Foo` matches a `soap:Envelope/soap:
Body/Foo` document without forcing the user to spell the namespace
prefix every time. Exact-match (`soap:Envelope/...`) still works since
both sides are local-stripped.

Counts move 268 -> 269 available, 24 -> 23 planned.