Breaking: xml 7, SDK floor ^3.11.0, raised dependency floors.
Adds RFC 3744 access control, RFC 3253 versioning, RFC 5842 bind,
RFC 6578 sync-collection and a raw request escape hatch.
Fixes Destination/If header percent-encoding and the cancel-path cleanup.

dart analyze --fatal-infos clean, 602 tests pass, publish dry-run 0 warnings.