Add model client sessions (#9102)

Maintain a long-running session.

codex-rs/Cargo.lock

@@ -984,8 +984,10 @@ dependencies = [
  "thiserror 2.0.17",
  "tokio",
  "tokio-test",
+ "tokio-tungstenite",
  "tokio-util",
  "tracing",
+ "url",
  "wiremock",
 ]
 
@@ -2126,6 +2128,7 @@ dependencies = [
  "codex-protocol",
  "codex-utils-absolute-path",
  "codex-utils-cargo-bin",
+ "futures",
  "notify",
  "pretty_assertions",
  "regex-lite",
@@ -2134,6 +2137,7 @@ dependencies = [
  "shlex",
  "tempfile",
  "tokio",
+ "tokio-tungstenite",
  "walkdir",
  "wiremock",
 ]
@@ -2361,6 +2365,12 @@ dependencies = [
  "syn 2.0.104",
 ]
 
+[[package]]
+name = "data-encoding"
+version = "2.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7a1e2f27636f116493b8b860f5546edb47c8d8f8ea73e1d2a20be88e28d1fea"
+
 [[package]]
 name = "dbus"
 version = "0.9.9"
@@ -7117,6 +7127,18 @@ dependencies = [
  "tokio-stream",
 ]
 
+[[package]]
+name = "tokio-tungstenite"
+version = "0.21.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c83b561d025642014097b66e6c1bb422783339e0909e4429cde4749d1990bc38"
+dependencies = [
+ "futures-util",
+ "log",
+ "tokio",
+ "tungstenite",
+]
+
 [[package]]
 name = "tokio-util"
 version = "0.7.18"
@@ -7511,6 +7533,25 @@ dependencies = [
  "ratatui-core",
 ]
 
+[[package]]
+name = "tungstenite"
+version = "0.21.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ef1a641ea34f399a848dea702823bbecfb4c486f911735368f1f137cb8257e1"
+dependencies = [
+ "byteorder",
+ "bytes",
+ "data-encoding",
+ "http 1.3.1",
+ "httparse",
+ "log",
+ "rand 0.8.5",
+ "sha1",
+ "thiserror 1.0.69",
+ "url",
+ "utf-8",
+]
+
 [[package]]
 name = "typenum"
 version = "1.18.0"