fix: resolve module-alias-qualified type in reflection arg slot (issue 0147)

size_of(sel.Selection) and the other reflection builtins rejected a
module-alias-qualified type: in argument position it parses as a .field_access
expression (not the dotted .type_expr a declaration produces), and neither
isStaticTypeArg nor resolveTypeArg had a .field_access arm. Add both: a pure
namespace-decl scan in isStaticTypeArg, and resolution via namespaceAliasTarget
+ resolveNominalLeaf in the target module context in resolveTypeArg (mirroring
the value-position lowerFieldAccess path). No fabricated-stub fallback.

Regression: examples/0192-types-size-of-qualified-alias.sx

examples/expected/0192-types-size-of-qualified-alias.exit

@@ -0,0 +1 @@
+0

examples/expected/0192-types-size-of-qualified-alias.stderr

@@ -0,0 +1 @@
+

examples/expected/0192-types-size-of-qualified-alias.stdout

@@ -0,0 +1,2 @@
+size=12
+sum=6