Restore a clean Rust workspace quality baseline

[arniber21]

What to build

Restore the current Rust checkout to a deterministic green baseline before further feature work. The audit found formatting drift, two Clippy errors, and five neutral-atom snapshot failures; the failed test run also left hundreds of tests unexecuted.

Acceptance criteria

• Workspace formatting passes without modifying files during the check.
• Workspace Clippy passes for all non-Flux targets with warnings denied.
• The complete fast workspace test run passes, including every neutral-atom stats and resource-report snapshot.
• Snapshot changes are reviewed as intentional behavior changes, not blindly accepted.
• No tests remain unexecuted because the runner stopped after an earlier failure.

Blocked by

None - can start immediately.

[arniber21]

Implemented and merged via PR. Closing as complete.