chore: rename codex-command to codex-shell-command (#11378)

This addresses some post-merge feedback on
https://github.com/openai/codex/pull/11361:

- crate rename
- reuse `detect_shell_type()` utility

codex-rs/shell-command/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "codex-shell-command"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[lints]
+workspace = true
+
+[dependencies]
+base64 = { workspace = true }
+codex-protocol = { workspace = true }
+codex-utils-absolute-path = { workspace = true }
+once_cell = { workspace = true }
+regex = { workspace = true }
+serde = { workspace = true, features = ["derive"] }
+serde_json = { workspace = true }
+shlex = { workspace = true }
+tree-sitter = { workspace = true }
+tree-sitter-bash = { workspace = true }
+url = { workspace = true }
+which = { workspace = true }
+
+[dev-dependencies]
+anyhow = { workspace = true }
+pretty_assertions = { workspace = true }