Enable rustyline read-ahead buffer preservation (#9382)

Enable buffer-redux on the workspace rustyline dependency and add its
locked buffer-redux 1.1.0 dependency. Keep existing dependency versions
and checksums, including nix, libc and rustix, unchanged.

RustPython retains a rustyline Editor across interactive prompts. On
Unix, this feature lets a successful readline submission save unread
buffered input for the next read instead of dropping the old reader's
buffer. This is based on the source call chain, not a runtime reproduction.

Assisted-by: OpenAI Codex:model version unavailable

Cargo.lock

@@ -448,6 +448,15 @@ dependencies = [
  "serde_core",
 ]
 
+[[package]]
+name = "buffer-redux"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "431a9cc8d7efa49bc326729264537f5e60affce816c66edf434350778c9f4f54"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "bumpalo"
 version = "3.20.3"
@@ -4209,6 +4218,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "53f6a737db68eb1a8ccff86b584b2fc13eca6a7bb6f78ebc7c529547e3ab9684"
 dependencies = [
  "bitflags 2.13.2",
+ "buffer-redux",
  "cfg-if",
  "clipboard-win",
  "home",

Cargo.toml

@@ -296,7 +296,7 @@ rustls-graviola = "0.4"
 rustls-native-certs = "0.8"
 rustls-pemfile = "2.2"
 rustls-webpki = { version = "0.103", default-features = false, features = ["std"] }
-rustyline = "18"
+rustyline = { version = "18", features = ["buffer-redux"] }
 serde = { package = "serde_core", version = "1.0.225", default-features = false, features = ["alloc"] }
 schannel = "0.1.29"
 scopeguard = "1"