Track crossbeam-epoch 0.10 release and re-enable Miri rayon tests

[dchud]

Summary

After #47 skips rayon tests under Miri (due to a known stacked borrows UB in crossbeam-epoch 0.9.18), we need to track the upstream fix and re-enable those tests.

What to watch

• Upstream tracking issue: crossbeam-rs/crossbeam#1181
• Blocking issue: crossbeam-rs/crossbeam#946
• Current version: crossbeam-epoch 0.9.18 (via rayon 1.11.0)
• Target version: crossbeam-epoch 0.10.x (once released)

When to act

Once crossbeam-epoch 0.10 ships:

1. Update Cargo.lock (likely via a rayon update)
2. Remove #[cfg_attr(miri, ignore)] from the 4 rayon tests in src/rayon_parser_pool.rs
3. Verify Miri CI passes with rayon tests included

Context

See #47 for the full Miri error analysis.

[dchud]

Bead: mrrc-3ivc