Rust port: wss:// dial panics on Linux (no process-level rustls CryptoProvider) #66

Found while writing the conformance negatives in #62 (refs #24).

In poc/reverse-attach-linux, a reverse-attach dial to a wss:// runtime panics inside tungstenite::connect: rustls has no process-level CryptoProvider installed, so TLS setup panics instead of returning an error. A wss:// runtime would therefore panic the dial thread rather than end the grant with a TLS error.

The test attach::client::tests::wss_to_a_plaintext_listener_fails_without_falling_back currently accepts that panic as a failed dial, so it proves only that no plaintext HTTP is sent, not that TLS is attempted.

Fix candidates: install a default provider at startup (rustls::crypto::ring::default_provider().install_default() or the aws-lc equivalent), or enable exactly one rustls crypto feature so the default is picked automatically. Then tighten the test to require a TLS error, not a panic, and add the successful-wss handshake row in docs/parity-checklist.md once a TLS fixture exists.