fix(tls): trust the OS certificate store on relay WebSocket connections

[benjaminkitt]

Problem

The desktop app's relay WebSocket trusts only a compiled-in Mozilla root list and ignores the OS trust store, so Buzz cannot connect to a relay from a machine behind a TLS-inspecting proxy (Netskope, Zscaler, Palo Alto, …). The connection fails with:

invalid peer certificate: UnknownIssuer

There is no user- or admin-side workaround: installing the corporate CA into the system keychain has no effect, and neither SSL_CERT_FILE nor NODE_EXTRA_CA_CERTS is consulted on this path.

This is easy to misdiagnose, because everything else in the app works. HTTPS requests go through reqwest, which uses rustls-platform-verifier and does read the OS trust store. Only the WebSocket path is affected, so the app looks healthy right up until the relay never connects.

Root cause

1. desktop/src-tauri/Cargo.toml and the root Cargo.toml build tokio-tungstenite with only the rustls-tls-webpki-roots feature. rustls-tls-native-roots is not enabled anywhere in the workspace, so feature unification does not compensate.
2. desktop/src-tauri/src/native_websocket.rs calls bare connect_async(url) with no custom Connector, so tokio-tungstenite builds its default root store — which under that feature set is the bundled Mozilla roots only.
3. desktop/src/shared/api/relayClientSession.ts and readOnlyRelayClient.ts reach the relay via invoke("plugin:websocket|connect"), so relay traffic goes through the Rust path above rather than the webview. (The webview would have used the OS trust store and would not have this problem.)

The same applies to the workspace dependency, so buzz, buzz-acp and buzz-dev-mcp are affected too. buzz-agent uses reqwest only and is unaffected.

Confirmed against a v0.5.0 release build: the binary contains the Mozilla root names (ISRG Root X1, DigiCert Global Root G2, …) and contains SecTrustEvaluateWithError (rustls-platform-verifier, via reqwest) but no rustls_native_certs / load_native_certs symbols.

Fix

Enable rustls-tls-native-roots alongside the existing feature, in both manifests.

The two root-store features are additive — tokio-tungstenite's src/tls.rs pushes both sets into the same RootCertStore, and the webpki branch is not gated on not(rustls-tls-native-roots). So this preserves today's behaviour for everyone (the bundled Mozilla roots are still there) and additionally honours the platform trust store.

Verification

Reproduced with a standalone tokio-tungstenite 0.29 probe against a real proxied relay, connecting with each root store in turn:

(a) webpki-roots only      => FAILED: invalid peer certificate: UnknownIssuer
    native cert load: added=148 ignored=0 errors=[]
(b) native + webpki roots  => SUCCESS (TLS + WS handshake completed)

I then built the full app from this branch and confirmed the relay connects normally on the affected machine, and that the rebuilt buzz / buzz-acp / buzz-dev-mcp sidecars pick up the change through the workspace dependency.

Alternative worth considering

Since the app already depends on rustls-platform-verifier through reqwest, an arguably tidier fix is to build a Connector::Rustls from the platform verifier and pass it to connect_async_tls_with_config. That would make WebSocket trust behaviour match HTTP trust behaviour instead of having the two paths use different trust stores. Happy to rework this PR that way if you'd prefer it.

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