fix: add explicit toolchain input for pinned rust-toolchain action

When dtolnay/rust-toolchain is pinned to a SHA instead of a branch
name, the toolchain version can't be inferred from the ref and must
be passed explicitly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mikolalysenko

.github/workflows/ci.yml

@@ -18,6 +18,7 @@ jobs:
       - name: Install Rust
         uses: dtolnay/rust-toolchain@efa25f7f19611383d5b0ccf2d1c8914531636bf9 # stable
         with:
+          toolchain: stable
           components: clippy
 
       - name: Cache cargo

.github/workflows/release.yml

@@ -42,6 +42,7 @@ jobs:
       - name: Install Rust
         uses: dtolnay/rust-toolchain@efa25f7f19611383d5b0ccf2d1c8914531636bf9 # stable
         with:
+          toolchain: stable
           targets: ${{ matrix.target }}
 
       - name: Install cross