feat(dev/tunnel): WSS client + frame protocol (Phase 1, no integration yet)

Adds the WebSocket side of `mirrorstack dev`:
  - Frame envelope (type, id, corr_id, stream_id, payload) — wire-shape
    matches api-platform's internal/dispatch/ws/frames.go
  - Connect: opens wss_url?token=ttok, sends register, awaits register_ack
  - Background task: pings every 30s, replies to server pings, sends
    close frame on shutdown signal

Deferred frame types (rpc.*, sql.*) are enumerated in the FrameType enum
so server frames of those shapes deserialize without forcing a reconnect
once those planes go live.

This module is `#[allow(dead_code)]` for now — it compiles + tests but
isn't wired into the dev lifecycle yet. End-to-end integration requires
two pieces still in flight elsewhere:
  - api-platform AWS Sender impl (apigatewaymanagementapi.PostToConnection)
  - IaC for the WS API GW + Lambda routing

Once those land, a small follow-up PR plugs this module into dev::run
and adds a --tunnel flag that gates the connect.

Deps added (used only inside this module):
  - tokio (rt + macros + time + sync + net + io-util)
  - tokio-tungstenite (connect + rustls-tls-webpki-roots)
  - futures-util (sink + std)

Test plan:
- [x] cargo test (4 new round-trip + uniqueness tests)
- [x] cargo clippy --all-targets -- -D warnings clean
- [x] cargo fmt --all -- --check clean

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

Author: I-am-nothing

Cargo.lock

@@ -29,6 +29,9 @@ dialoguer = { version = "0.11", default-features = false }
 console = "0.15"
 indicatif = "0.17"
 ctrlc = "3"
+tokio = { version = "1", features = ["rt", "macros", "time", "sync", "net", "io-util"] }
+tokio-tungstenite = { version = "0.24", default-features = false, features = ["connect", "rustls-tls-webpki-roots"] }
+futures-util = { version = "0.3", default-features = false, features = ["sink", "std"] }
 
 [dev-dependencies]
 mockito = "1.6"

Cargo.toml

@@ -22,6 +22,11 @@ use super::{ok_mark, warn_prefix};
 
 mod compose;
 mod process;
+// Used in a follow-up PR that integrates WSS into the dev lifecycle.
+// Compiled + tested now so the wire format and protocol stay correct
+// while the AWS Sender impl + IaC for the WS API GW catch up.
+#[allow(dead_code)]
+mod tunnel;
 
 #[derive(Args)]
 pub struct DevArgs {