feat: Run cargo shear during CI (#3338)

Run cargo shear as part of the CI to ensure no unused dependencies

codex-rs/mcp-server/tests/common/Cargo.toml

@@ -9,20 +9,16 @@ path = "lib.rs"
 [dependencies]
 anyhow = "1"
 assert_cmd = "2"
-codex-core = { path = "../../../core" }
 codex-mcp-server = { path = "../.." }
 codex-protocol = { path = "../../../protocol" }
 mcp-types = { path = "../../../mcp-types" }
 pretty_assertions = "1.4.1"
 serde = { version = "1" }
 serde_json = "1"
-shlex = "1.3.0"
-tempfile = "3"
 tokio = { version = "1", features = [
     "io-std",
     "macros",
     "process",
     "rt-multi-thread",
 ] }
-uuid = { version = "1", features = ["serde", "v4"] }
 wiremock = "0.6"