fix: verify runner-owned Rust toolchain path

Author: Bnjoroge1

crates/preloop-orchestrator/src/environment.rs

@@ -243,7 +243,7 @@ impl ToolchainLayer {
             Self::Rust(channel) => {
                 let channel = safe_component(channel);
                 format!(
-                    "export RUSTUP_HOME=/home/runner/.rustup CARGO_HOME=/home/runner/.cargo && \
+                    "export RUSTUP_HOME=/home/runner/.rustup CARGO_HOME=/home/runner/.cargo PATH=/home/runner/.cargo/bin:$PATH && \
                      command -v cargo >/dev/null && \
                      rustup run {channel} rustc --version >/dev/null && \
                      rustup run {channel} cargo-fmt --version >/dev/null && \