fix(ci): re-pin rust-ci-reusable past toolchain-input breakage (#8)

Re-pins rust-ci-reusable.yml from d135b05bfc647d0c0fbfedc7e80f37ea50f49236 (pre-fix) to 412a7031577112b31ee287cc6060179d638d6500 (standards main).
The old SHA predates standards#439, which added the mandatory `toolchain: stable`
input to the SHA-pinned dtolnay/rust-toolchain step. Without it, all four rust-ci
jobs fail fast with `'toolchain' is a required input`. This restores Rust CI.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/rust-ci.yml

@@ -11,4 +11,4 @@ permissions:
   contents: read
 jobs:
   rust-ci:
-    uses: hyperpolymath/standards/.github/workflows/rust-ci-reusable.yml@d135b05bfc647d0c0fbfedc7e80f37ea50f49236
+    uses: hyperpolymath/standards/.github/workflows/rust-ci-reusable.yml@412a7031577112b31ee287cc6060179d638d6500