feat(lsp): warn on undeclared block templates and addresses

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.

server/src/tools/def_flow.py

@@ -338,3 +338,27 @@ def derived_def_symbol(
         targets.extend(target for variable in variables for target in scope_targets.get(variable, ()))
     kinds = frozenset(kind for target in targets for kind in _target_kinds(target, table, namespace))
     return (kinds, *literal) if kinds else None
+
+
+def _all_commands(node: Node) -> Iterator[Command]:
+    for child in getattr(node, "children", []):
+        if isinstance(child, Command):
+            yield child
+        yield from _all_commands(child)
+
+
+def unknown_def_names(tree: Node, declared: dict[str, frozenset[str]]) -> list[tuple[str, str, lsp.Range]]:
+    """Literal NX command arguments naming a block template or address no .def file declares.
+
+    ``declared`` maps each kind to its declared names; kinds without any
+    declaration are not checked, since their .def file is not loaded.
+    """
+    unknown = []
+    for command in _all_commands(tree):
+        for node, kind in def_argument_kinds(command):
+            names = declared.get(kind)
+            name = def_name(node) if names else None
+            if name is not None and name not in names:
+                line, column = node.contents_pos
+                unknown.append((kind, name, _range(line, column, name)))
+    return unknown