fix: MSRV 1.94 exclusively + toolchain components + backend features

- rust-toolchain.toml: add components = ["clippy", "rustfmt"]
- ci.yaml: MSRV 1.64.0 → 1.94.0, BLAS_MSRV 1.71.1 → 1.94.0
  (code uses LazyLock 1.80, is_multiple_of 1.94 — 1.64 was broken)
- Cargo.toml: native/intel-mkl/openblas = ["std"]
  (backend features need std for hpc module with LazyLock dispatch)
- Removed duplicate openblas = [] declaration

https://claude.ai/code/session_01NYGrxVopyszZYgLBxe4hgj

Author: claude

.github/workflows/ci.yaml

@@ -15,8 +15,8 @@ env:
   HOST: x86_64-unknown-linux-gnu
   FEATURES: "approx,serde,rayon"
   RUSTFLAGS: "-D warnings -C target-cpu=x86-64-v3"
-  MSRV: 1.64.0
-  BLAS_MSRV: 1.71.1
+  MSRV: 1.94.0
+  BLAS_MSRV: 1.94.0
 
 jobs:
   pass-msrv:

Cargo.toml

@@ -105,9 +105,9 @@ jit-native = ["jitson", "dep:cranelift-codegen", "dep:cranelift-jit", "dep:crane
 
 
 # HPC backend feature gates (mutually exclusive)
-native = []
-intel-mkl = []
-openblas = []
+native = ["std"]
+intel-mkl = ["std"]
+openblas = ["std"]
 
 # no_std polyfill for `static LazyLock` in `src/simd.rs` (sprint A12).
 # Pulls in `portable-atomic` with the `critical-section` impl plus the

rust-toolchain.toml

@@ -1,2 +1,3 @@
 [toolchain]
 channel = "1.94.0"
+components = ["clippy", "rustfmt"]