Automatic toolchain upgrade to nightly-2025-10-18 (#4418)

Update Rust toolchain from nightly-2025-10-17 to nightly-2025-10-18
without any other source changes.

Co-authored-by: tautschnig <1144736+tautschnig@users.noreply.github.com>

Author: github-actions[bot]

rust-toolchain.toml

@@ -2,5 +2,5 @@
 # SPDX-License-Identifier: Apache-2.0 OR MIT
 
 [toolchain]
-channel = "nightly-2025-10-17"
+channel = "nightly-2025-10-18"
 components = ["llvm-tools", "rustc-dev", "rust-src", "rustfmt"]