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.

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