test(0140): pin comptime type-construction bail diagnostic (examples/1179)

Move the issue 0140 repro into the feature suite as a regression test.
Asserts the build-gating diagnostic 'comptime type construction failed:
comptime define(): enum has no variants' at the construction site, exit
1 — locking out the prior 'unresolved type reached LLVM emission' panic.

issues/0140-comptime-type-construction-bail-unresolved-panic.sx

@@ -1,20 +0,0 @@
-// Repro for issue 0140 — a FAILING comptime type construction
-// (`define` with an empty variant list) bails correctly in the interp
-// ("comptime define(): enum has no variants"), but that bail is swallowed:
-// `evalComptimeType` returns null, the decl is poisoned to `.unresolved`
-// with NO diagnostic, and the `.unresolved` type reaches LLVM emission and
-// PANICS ("unresolved type reached LLVM emission") instead of surfacing a
-// clean error with the bail reason.
-//
-// Expected: a build-time diagnostic at the construction site naming the
-// bail reason (e.g. "comptime type construction failed: enum has no
-// variants"), exit 1, no panic.
-#import "modules/std.sx";
-#import "modules/std/meta.sx";
-
-Empty :: define(declare("Empty"), .enum(.{ variants = .[] }));
-
-main :: () -> i32 {
-    e : Empty = ---;
-    return 0;
-}