chore: cargo fmt --all

[shaal]

Run cargo fmt --all on the workspace. Pure reformatting — no semantic changes.

Why

cargo fmt --all -- --check is currently failing on main (see e.g. Workspace CI on PR #368, job 72434376746 — 430 files / 3342 diff sections flagged). This brings the tree back into compliance so the CI gate passes without each feature PR having to absorb the debt.

Scope

• 430 .rs files reformatted across 29 crates and 25 examples.
• Staged with git add '*.rs' — nothing else touched.
• Locally verified: cargo fmt --all -- --check now exits 0.

Follow-up

Once merged, rebase in-flight PRs (e.g. #368) on main to clear their inherited fmt failure. Merge conflicts should be whitespace-only and resolvable by re-running cargo fmt post-rebase.