Reformats the Rust tree with `cargo fmt` under the re-pinned toolchain
(rustc 1.95.0 / rustfmt 1.9.0), addressing the formatting drift that has
been failing the **Cargo fmt** job of Rust CI on `main` (run 28516280339
class failures) since the 2026-07-01 re-pin (#292).

Before: `cargo fmt --check` reported 129 diffs across 85 files. This PR
commits the fmt output for **21 of those 85 files** — pure
whitespace/wrapping changes, no semantic edits.

**Partial-scope caveat**: the remaining 64 files (all of
`src/rust/provers/*.rs` in the fmt set, plus
`src/interfaces/graphql/{schema,resolvers}.rs`) also have fmt drift, but
their headers carry a non-canonical owner line (`ECHIDNA Project Team`,
no `Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>`), so the repo
pre-commit licence hook rejects them. Licence-header edits are
owner-gated (per CLAUDE.md: historical drift on individual files is
owner-managed, not reconciled in routine PRs), so those files are
excluded here and the `Cargo fmt` job will remain red until their
headers are owner-reconciled (or fmt-committed by the owner). Full list
in the PR discussion below if needed; `src/rust/main.rs` was never in
the fmt set.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>