The nightly workflow has failed every run since it was added. Fix the
four distinct issues so it can actually exercise the slow checks:
- cargo-mutants: drop bogus `--in-diff-base ""` flag (never existed in
cargo-mutants; v27 rejects it).
- fuzz smoke: pin `--target x86_64-unknown-linux-gnu`. Binstall ships a
musl-static cargo-fuzz binary whose default target inherits its own
triple, and libfuzzer's sanitizer is incompatible with `crt-static`.
- miri: move multi-module filters after `--`. `cargo test` only accepts
one TESTNAME positional; libtest accepts multiple substring filters.
- stateright random_large: add `target_state_count(1_000_000)` so the
simulation actually terminates instead of looping past the 30 min CI
timeout. The comment already claimed "up to 10⁶ states".
Also refreshes fuzz/Cargo.lock, regenerated by the local verification
build (was stale vs. parent deps).
swaits
2c28dd77b4