Add visible v1 diagnostics guardrails

src/main.zig

@@ -1,5 +1,6 @@
 const std = @import("std");
 const context_mod = @import("context.zig");
+const diagnostics = @import("diagnostics.zig");
 const input = @import("input.zig");
 const job = @import("job.zig");
 const layout = @import("layout.zig");
@@ -224,6 +225,7 @@ fn collectRemainingArgs(allocator: std.mem.Allocator, args: *std.process.Args.It
 
 test {
     _ = context_mod;
+    _ = diagnostics;
     _ = input;
     _ = job;
     _ = layout;