imports: retire the is_pub sketch on NamespaceTarget

Every namespace alias is module surface under the carry rule — the
planned pub-import front-end form is superseded; no per-edge visibility
flag is needed.

src/imports.zig

@@ -482,14 +482,13 @@ pub const ModuleDecls = std.StringHashMap(ModuleRawDeclIndex);
 
 /// One namespace import edge: `alias :: #import "…"` (or `alias :: #import c …`).
 /// `target_module_path` is captured at resolution time (otherwise lost — it is
-/// not derivable from the namespace node alone). `is_pub` stays false until the
-/// `pub`-import phase lands the front-end form.
+/// not derivable from the namespace node alone). Every alias is module surface
+/// under the carry rule — there is no per-edge visibility flag.
 pub const NamespaceTarget = struct {
     alias: []const u8,
     importer_source: []const u8,
     target_module_path: []const u8,
     own_decls: []const *Node,
-    is_pub: bool = false,
     /// The `DeclId` of each member in `own_decls`, in slice order. Filled by
     /// `buildDeclTable` (empty until then). Lets a member be addressed by stable
     /// id without re-deriving it from the node pointer.