`Quality / Check formatting` CI lane was broken on `main` after the
6-channel-removal PR (#5265) landed: the deletions in that PR
shortened several match arms and function signatures enough that
rustfmt now wants the re-flowed form, but the PR merged before its
own followup fmt commit could land.

This commit is the exact rustfmt diff from the failed CI job
applied verbatim to main:

- `crates/librefang-api/src/routes/channels.rs`:
  alphabetical sort of `use super::sidecar_describe` vs
  `use super::skills`; `webhook_route_suffix` match arms collapsed
  to fewer lines; `secrets_env_keys` read re-indented to the
  single-call form; `upsert_secret(...).map_err(|e| {…})?`
  collapsed.
- `crates/librefang-api/src/routes/secrets_env.rs`:
  `parent.join(format!(...))` fits on one line.
- `crates/librefang-api/src/routes/sidecar_describe.rs`:
  `describe_sidecar(command, args)` signature on one line.
- `crates/librefang-api/tests/channels_routes_test.rs`:
  `vec![SidecarSchemaField {...}]` re-formatted to the multi-line
  `vec![\n    Struct { ... },\n]` form rustfmt prefers for single
  big literals.
- `crates/librefang-api/tests/sidecar_describe_test.rs`:
  `describe_sidecar("python3", &[...]).await` collapsed.
- `crates/librefang-channels/src/sidecar.rs`:
  `build_spawn_env(home, ctx)` and `SidecarTask::new(config, home)`
  signatures collapsed; the `assert_eq!` chain in the test re-flowed
  because the new `got.get(...).map(|s| s.as_str())` chain doesn't
  fit the single-line form inside `assert_eq!(...)`.
- `crates/librefang-types/tests/config_default_roundtrip.rs`:
  re-flow the import list now that `LinkedInConfig` is gone; drop
  the double blank line after `voice_config_default_roundtrips_*`.

No logic changes — pure rustfmt diff.