Fuzzer Failure

**Repro:**
```
bazel test -c opt //xls/fuzzer:run_crasher_test_2026-05-06_cad8.x
```

**Error Message:**
```
E0506 06:07:07.944470 1898540 sample_runner.cc:831] Exception when running sample: INVALID_ARGUMENT: SampleError: Result miscompare for sample 33:
args: bits[16]:0x8000; bits[10]:0x155; bits[10]:0x20; bits[23]:0x2_0000
evaluated opt IR (JIT), evaluated unopt IR (JIT) =
(bits[10]:0x155, bits[4]:0x0, bits[1]:0x0, bits[2048]:0x0)
evaluated opt IR (interpreter), evaluated unopt IR (interpreter), interpreted DSLX =
(bits[10]:0x155, bits[4]:0xf, bits[1]:0x0, bits[2048]:0x0)
== STACK ==
@ 0x7fb6f663d6cc (xls::CompareResultsFunction())
@ 0x7fb6f6a5cf19 (xls::SampleRunner::RunFunction())
@ 0x7fb6f6a57ad9 (xls::SampleRunner::RunFromFiles())
@ 0x7fb6f830b4f2 (xls::RunSample())
@ 0x7fb6f830ce58 (xls::GenerateSampleAndRun())
@ 0x7fb6f871a0dd (xls::(anonymous namespace)::FuzzIntegrationTest_Fuzzing_Test::TestBody())
@ 0x7fb66549a52a (testing::Test::Run())
@ 0x7fb66549bdc3 (testing::TestInfo::Run())
@ 0x7fb66549d117 (testing::TestSuite::Run())
@ 0x7fb6654b1aed (testing::internal::UnitTestImpl::RunAllTests())
@ 0x7fb6654b0738 (testing::UnitTest::Run())
@ 0x7fb6c93309ef (main)
@ 0x7fb614242f12 (__libc_start_main)
@ 0x5555f6444b2a (../sysdeps/x86_64/start.S:122 _start)
E0506 06:07:07.971976 1898540 run_fuzz.cc:278] Sample failed: INVALID_ARGUMENT: SampleError: Result miscompare for sample 33:
args: bits[16]:0x8000; bits[10]:0x155; bits[10]:0x20; bits[23]:0x2_0000
evaluated opt IR (JIT), evaluated unopt IR (JIT) =
(bits[10]:0x155, bits[4]:0x0, bits[1]:0x0, bits[2048]:0x0)
evaluated opt IR (interpreter), evaluated unopt IR (interpreter), interpreted DSLX =
(bits[10]:0x155, bits[4]:0xf, bits[1]:0x0, bits[2048]:0x0)
=== Source Location Trace: ===
third_party/xls/fuzzer/cpp_sample_runner.cc:119
third_party/xls/fuzzer/run_fuzz.cc:233
```