fix: Change unknown bun:bundle export from warning to error

- Unknown exports from "bun:bundle" now produce an error instead of a warning
- Remove unnecessary comment in visitStmt.zig

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/ast/P.zig

@@ -2679,8 +2679,7 @@ pub fn NewParser_(
                         const ref = try p.declareSymbol(.other, item.name.loc, name);
                         p.bundler_feature_flag_ref = ref;
                     } else {
-                        // Warn about unknown specifiers
-                        try p.log.addWarningFmt(p.source, item.alias_loc, p.allocator, "\"bun:bundle\" only exports \"feature\"; \"{s}\" will be undefined", .{item.alias});
+                        try p.log.addErrorFmt(p.source, item.alias_loc, p.allocator, "\"bun:bundle\" has no export named \"{s}\"", .{item.alias});
                     }
                 }
                 // Return empty statement - the import is completely removed

src/ast/visitStmt.zig

@@ -40,9 +40,6 @@ pub fn VisitStmt(
 
         const visitors = struct {
             pub fn s_import(noalias p: *P, noalias stmts: *ListManaged(Stmt), noalias stmt: *Stmt, noalias data: *S.Import) !void {
-                // Note: `import { feature } from "bun:bundle"` is handled at parse time
-                // in processImportStatement(), not here at visit time.
-
                 try p.recordDeclaredSymbol(data.namespace_ref);
 
                 if (data.default_name) |default_name| {