`PyMutex` is built on `RawCellMutex` on single-threaded targets (iOS,
Android, wasm32) and is not `Sync`, so a `static PyMutex<...>` fails to
compile. `PyTypeRef` is also not `Send` by default, which compounds the
issue.

Replace the static parameter-type registry with class-name comparison
(`"CompressionParameter"` / `"DecompressionParameter"`). The two names
originate from the `compression.zstd` module we ship, so identity vs.
name comparison is equivalent in practice. `set_parameter_types` now
just validates that its arguments are type objects.

Verified locally:
- `cargo build -p rustpython-stdlib` (default features): clean.
- `cargo check -p rustpython-stdlib --no-default-features --features host_env`
  (simulates iOS by dropping the `threading` feature): clean.
- `cargo run -- -m test test_zstd`: 119 tests pass, 1 expected failure.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

RustPython's clippy lint set rejects `std::` imports for items that also
live in `core::` or `alloc::`. Switch every such reference in `zstd.rs`:

- `std::ffi::{c_int, CStr}`        -> `core::ffi::{c_int, CStr}`
- `std::fmt::*`                    -> `core::fmt::*`
- `std::slice::from_raw_parts`     -> `core::slice::from_raw_parts`
- `std::borrow::Cow`               -> `alloc::borrow::Cow`

Also clear up other clippy findings under `-D warnings`:

- Drop the redundant `obj.clone()` on the last use of `obj` in
  `parse_zstd_dict_arg`.
- Collapse `.map(|n| n.get()).unwrap_or(0)` to `.map_or(0, |n| n.get())`
  in the two dict-id readers.
- Replace `&*work_data` with `&work_data` (auto-deref).
- Factor the `(Option<Digested>, Option<PyRef<ZstdDict>>)` return shape
  into a `DictLoadResult<D>` type alias to satisfy `type_complexity`.
- Replace the remaining `std::mem::transmute<u32, ZSTD_cParameter>` /
  `ZSTD_dParameter` in `get_param_bounds` with the existing safe
  `c_param_enum` / `d_param_enum` helpers; surfaces a clear "invalid
  parameter" `ValueError` instead of relying on UB-adjacent transmutes
  for unknown ints.

Verified locally:
- `cargo clippy -p rustpython-stdlib --no-deps -- -Dwarnings`: clean
  (only the pre-existing `socket.rs::sock_wait` warning remains).
- `cargo run -- -m test test_zstd`: 119 pass, 1 expected failure.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

The previous run's `Lint` job failed with a `401 Unauthorized` from
reviewdog hitting the GitHub API (a transient CI/permissions issue,
unrelated to this PR's diff). Pushing an empty commit to re-run CI.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

{"subject": "Format zstd module and extend spell-check ignores", "body": "- Apply rustfmt formatting to zstd.rs\n- Add additional spell-checker ignore entries for zstd identifiers"}

Co-authored-by: Shahar Naveh <50263213+ShaharNaveh@users.noreply.github.com>

{"subject": "Remove rustdoc comments from zstd module", "body": "- Strip doc comments from internal items in _zstd module\n- Convert a few API-doc comments into regular implementation notes where appropriate"}

- Have set_parameter_types stash the CompressionParameter/DecompressionParameter classes as private _zstd module attributes instead of validating and discarding them
- check_wrong_param_kind now compares key classes by identity against the registered type, matching CPython's Py_TYPE check, and skips when unregistered
- Error message names the actual key type as an attribute

- Raise TypeError (not RuntimeError), matching CPython, when both
  `level` and `options` are passed to ZstdCompressor
- Parse set_pledged_input_size's argument before taking the state lock
  so a re-entrant __index__ can't deadlock, and fix the off-by-one in
  its bound message to match CPython

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>