fix(ci): re-pin rust-ci-reusable.yml past the toolchain-required-input fix

Pinned SHA predated standards#439 (fix(rust-ci): pass explicit
toolchain: stable to SHA-pinned dtolnay action), so every run failed
at 'toolchain is a required input' before any real check executed.
Re-pinned to standards main tip (7c9db0e5), which is at/after #439.

Author: hyperpolymath

.github/workflows/rust-ci.yml

@@ -14,4 +14,4 @@ permissions:
 
 jobs:
   rust-ci:
-    uses: hyperpolymath/standards/.github/workflows/rust-ci-reusable.yml@d135b05bfc647d0c0fbfedc7e80f37ea50f49236
+    uses: hyperpolymath/standards/.github/workflows/rust-ci-reusable.yml@7c9db0e5909aab77bf11a444ade3b95c1d2b702e # re-pinned 2026-07-01: toolchain-required-input fix (standards#439)