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

.github/actions/build-bazel-package-binaries/action.yml

@@ -18,7 +18,7 @@ runs:
         cache-scope: bazel-release
 
     - name: Install Cargo for workspace metadata
-      uses: dtolnay/rust-toolchain@d124f86f28ff42855784ff3319f48ac182c248f8 # 1.99.1
+      uses: dtolnay/rust-toolchain@e081816240890017053eacbb1bdf337761dc5582 # 1.95.0
 
     - name: Configure MSVC environment
       if: ${{ runner.os == 'Windows' }}

.github/actions/build-cargo-package-binaries/action.yml

@@ -39,7 +39,7 @@ runs:
           *) echo "Unsupported build mode: $BUILD_MODE" >&2; exit 1 ;;
         esac
 
-    - uses: dtolnay/rust-toolchain@d124f86f28ff42855784ff3319f48ac182c248f8 # 1.99.1
+    - uses: dtolnay/rust-toolchain@e081816240890017053eacbb1bdf337761dc5582 # 1.95.0
       with:
         targets: ${{ inputs.target }}