Add diagnostics that warn when a literal NX command argument names a block
template or address that no loaded .def file declares (diagnostic codes
unknown-block-template and unknown-address). Names computed at runtime
(e.g. $var or "CYCLE_$x") are not checked, and kinds whose .def file is
not loaded are skipped.
The server now recomputes and refreshes diagnostics when .def documents
change (clears cached diagnostics and requests a workspace diagnostic
refresh if the client supports it). Tests cover positive, negative and
invalidated-cache cases.