Pin the Rust toolchain to 1.95.0 (#57373)

## What changed

- Replace Rust `1.99.1` pins with `1.95.0` across Cargo, Bazel, CI, release workflows, and Windows setup, and update the Bazel lockfile.
- Adjust Rust APIs, borrowing, and lint-related code for the pinned toolchain, and box MCP tool dispatch to bound compiler async-layout query depth.
- Update the halfwidth sound mark snapshot and allow optional symbol hash suffixes in the code mode host package smoke test.

GitOrigin-RevId: 75460c3d0465dc601811e619bce373a4f7ff2912

codex-rs/code-mode-protocol/src/grpc/mod.rs

@@ -1,5 +1,3 @@
-#![allow(clippy::double_must_use)] // Emitted by async_trait in the generated tonic service.
-
 #[cfg(codex_bazel)]
 pub use code_mode_proto::codex::code_mode::v1::*;