feat(ffi-linkage): postfix extern/export on #objc_class aggregate (Phase 3.1) — 1348 green

src/parser.zig

@@ -1406,6 +1406,23 @@ pub const Parser = struct {
         self.advance();
         try self.expect(.r_paren);
 
+        // Phase 3 (FFI-linkage): optional postfix `extern` / `export` after the
+        // `#objc_class("X")` directive — the new spelling that replaces the prefix
+        // `#foreign` modifier (mirrors `struct #compiler` postfix placement).
+        //   `… extern { … }`  ⇒ reference an existing runtime class (== `#foreign`).
+        //   `… export { … }`  ⇒ define + register a new sx class (== no `#foreign`).
+        // Maps straight onto the existing `is_foreign` decision so lowering is
+        // unchanged. The legacy prefix `#foreign` form still works via the
+        // `is_foreign` argument; interplay/diagnostics for combining them is Phase 4.
+        var is_foreign_eff = is_foreign;
+        if (self.current.tag == .kw_extern) {
+            is_foreign_eff = true;
+            self.advance();
+        } else if (self.current.tag == .kw_export) {
+            is_foreign_eff = false;
+            self.advance();
+        }
+
         try self.expect(.l_brace);
 
         var members = std.ArrayList(ast.ForeignClassMember).empty;
@@ -1633,7 +1650,7 @@ pub const Parser = struct {
             .foreign_path = foreign_path,
             .runtime = runtime,
             .members = try members.toOwnedSlice(self.allocator),
-            .is_foreign = is_foreign,
+            .is_foreign = is_foreign_eff,
             .is_main = is_main,
             .is_raw = name_is_raw,
         } });