Plain POSIX files: remove commit on close (fs.rs)

Staging every write until close broke tempfile, git, and SQLite, which
expect normal files. Actors that need an atomic publish write a temporary
file and rename it; the SDK has write_atomic for that.

cli/src/broker.rs

@@ -18,8 +18,7 @@ use tokio::sync::{mpsc, oneshot};
 use wasmtime::component::Component;
 
 use crate::candidate;
-use crate::fs::Mount;
-use crate::runtime::{InstanceConfig, Runtime};
+use crate::runtime::{InstanceConfig, Mount, Runtime};
 use crate::supervisor::{Control, Reply, Supervisor};
 use crate::world::{self, ActorMeta, NATIVE, VersionMeta, World};