"Access is denied" when running `cargo test` on Windows

When running cargo test -p spacetimedb-sdk on Windows, I'm getting tons of test failures like

---- rust::reconnect_same_address stdout ----
could not save config file: Access is denied. (os error 5)
Note: Using --project-path to provide a wasm file is deprecated, and will be
removed in a future release. Please use --wasm-file instead.
Uploading to local => http://127.0.0.1:3000
Publishing module...
thread 'rust::reconnect_same_address' panicked at crates\testing\src\lib.rs:38:10:
called `Result::unwrap()` on an `Err` value: Access is denied. (os error 5)

---- rust::delete_address stdout ----
could not save config file: Access is denied. (os error 5)
Note: Using --project-path to provide a wasm file is deprecated, and will be
removed in a future release. Please use --wasm-file instead.
Uploading to local => http://127.0.0.1:3000
Publishing module...
thread 'rust::delete_address' panicked at crates\testing\src\lib.rs:38:10:
called `Result::unwrap()` on an `Err` value: Access is denied. (os error 5)

---- rust::subscribe_all_select_star stdout ----
could not save config file: Access is denied. (os error 5)
Note: Using --project-path to provide a wasm file is deprecated, and will be
removed in a future release. Please use --wasm-file instead.
Uploading to local => http://127.0.0.1:3000
Publishing module...
thread 'rust::subscribe_all_select_star' panicked at crates\testing\src\lib.rs:38:10:
called `Result::unwrap()` on an `Err` value: Access is denied. (os error 5)

This has been happening for a couple of months now - I vaguely remember some changing to file locking - but I kept working around with --test-threads 1 so never raised this issue.

Run cargo test -p spacetimedb-sdk on Windows and inspect crates/testing/src/lib.rs:38, where the test setup unwraps the access-denied result. Compare the failures with the --test-threads 1 workaround and investigate the config-file save or locking behavior; done means the affected tests pass without requiring serialized execution.