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/0192-types-size-of-qualified-alias-mod.sx

@@ -0,0 +1,3 @@
+// Companion module for 0192 — exports `Selection`, a struct whose size is NOT 8
+// bytes (so a wrong fallback like `.i64` would be detectable).
+Selection :: struct { a: i32; b: i32; c: i32; }   // 12 bytes

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

@@ -0,0 +1,18 @@
+// `size_of(alias.Type)` on a module-alias-qualified type must resolve the type,
+// exactly as a declaration `: alias.Type` does. In argument position the
+// qualified name parses as a field-access expression; resolveTypeArg now
+// reconstructs the dotted name and resolves it through the alias map instead of
+// returning `.unresolved`.
+//
+// Regression (issue 0147).
+#import "modules/std.sx";
+sel :: #import "0192-types-size-of-qualified-alias-mod.sx";
+
+main :: () -> i32 {
+    // Qualified through the module alias, in a type-arg slot.
+    print("size={}\n", size_of(sel.Selection));   // 12
+    // Same name also resolves in a declaration (already worked).
+    s : sel.Selection = .{ a = 1, b = 2, c = 3 };
+    print("sum={}\n", s.a + s.b + s.c);            // 6
+    return 0;
+}

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