fuse: Don't expire directory entries in the kernel (#120)

Since AgentFS is the only writer to the SQLite-backed filesystem, the
kernel can cache metadata and directory entries indefinitely. When the
kernel initiates operations (create, unlink, rename, etc.), it already
knows about the changes and updates its cache from our replies - no
explicit invalidation is needed.

Author: penberg

cli/src/fuse.rs

@@ -17,7 +17,9 @@ use std::{
 };
 use tokio::runtime::Runtime;
 
-const TTL: Duration = Duration::from_secs(1);
+/// Cache entries never expire - we explicitly invalidate on mutations.
+/// This is safe because we are the only writer to the filesystem.
+const TTL: Duration = Duration::MAX;
 
 /// Options for mounting an agent filesystem via FUSE.
 #[derive(Debug, Clone)]