Use jemalloc for Linux musl binaries (#42850)

## What changed

- Configure the CLI and app server to use `tikv-jemallocator` on
  `x86_64-unknown-linux-musl` and `aarch64-unknown-linux-musl`.
- Keep the dependency and global allocator selection scoped to those targets.

GitOrigin-RevId: 93c54c90d9acb7e48edffd032cd8ec685a782210

codex-rs/app-server/Cargo.toml

@@ -114,6 +114,9 @@ tracing-subscriber = { workspace = true, features = ["env-filter", "fmt", "json"
 url = { workspace = true }
 uuid = { workspace = true, features = ["serde", "v7"] }
 
+[target.'cfg(all(target_os = "linux", target_env = "musl", any(target_arch = "x86_64", target_arch = "aarch64")))'.dependencies]
+tikv-jemallocator = { workspace = true }
+
 [target.'cfg(windows)'.dependencies]
 codex-windows-sandbox = { workspace = true }