Cap MessageStream buffer size to 1MB

We temporarily let it grow when the message size exceed the limit,
but restore the buffer's capacity shortly after. This ensures that,
for each connection in its entire lifetime, we only ever use 1MB.

crates/cli/Cargo.toml

@@ -16,7 +16,7 @@ anyhow = "1.0"
 clap = { version = "3.1", features = ["derive"] }
 dirs = "3.0"
 ipc-channel = "0.16"
-serde = { version = "1.0", features = ["derive"] }
+serde = { version = "1.0", features = ["derive", "rc"] }
 
 [target.'cfg(target_os = "macos")'.dependencies]
 core-foundation = "0.9"