ci: make CI genuinely green — rust-ci toolchain pin + fmt/clippy (#44)

## Summary

Make CI genuinely green. The shared rust-ci pin on `main` predates
standards#439, so the SHA-pinned `dtolnay/rust-toolchain` step errors
out before the job runs. This bumps the pin so rust-ci actually runs,
and brings the Rust sources to fmt + clippy(`-D warnings`) clean under
the CI toolchain (stable 1.96).

## Changes

- **rust-ci:** bump `rust-ci-reusable.yml` pin `d135b05` → `8dc2bf0`
(current `standards` HEAD; includes #439 toolchain fix + #441/#442).
- **Rust hygiene:** `cargo fmt` + `clippy --fix` where the repo had
pre-existing drift, so `cargo fmt --all -- --check` and `cargo clippy
--locked --all-targets -- -D warnings` pass.

## RSR Quality Checklist

### Required
- [x] Tests pass (`cargo test --locked --all-targets`)
- [x] Code is formatted (`cargo fmt --all -- --check`)
- [x] Linter is clean (`cargo clippy --locked --all-targets -- -D
warnings`)
- [x] No banned language patterns
- [x] SPDX license headers present on modified files
- [x] No secrets, credentials, or `.env` files included

## Testing

Verified locally with the CI toolchain (rustc/clippy/rustfmt 1.96.0):
`cargo fmt --check`, `clippy -D warnings`, `cargo check --locked`,
`cargo test --locked` all pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---
_Generated by [Claude
Code](https://claude.ai/code/session_01A6PSzJWpRxtzGDjUCEh7Mx)_

---------

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

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@8dc2bf039d1ff0372d650895c46bea7fbaec68ff

src/codegen/build_gen.rs

@@ -273,7 +273,8 @@ mod tests {
     #[test]
     fn test_build_script_contains_backend() {
         let manifest = test_manifest();
-        let script = generate_build_script(&manifest, Path::new("test-project.fut")).expect("TODO: handle error");
+        let script = generate_build_script(&manifest, Path::new("test-project.fut"))
+            .expect("TODO: handle error");
         assert!(script.contains("futhark opencl test-project.fut"));
         assert!(!script.contains("autotune"));
     }
@@ -282,14 +283,16 @@ mod tests {
     fn test_build_script_with_tuning() {
         let mut manifest = test_manifest();
         manifest.gpu.tuning = true;
-        let script = generate_build_script(&manifest, Path::new("test-project.fut")).expect("TODO: handle error");
+        let script = generate_build_script(&manifest, Path::new("test-project.fut"))
+            .expect("TODO: handle error");
         assert!(script.contains("futhark autotune"));
     }
 
     #[test]
     fn test_build_script_checks_futhark_installed() {
         let manifest = test_manifest();
-        let script = generate_build_script(&manifest, Path::new("test.fut")).expect("TODO: handle error");
+        let script =
+            generate_build_script(&manifest, Path::new("test.fut")).expect("TODO: handle error");
         assert!(script.contains("command -v futhark"));
     }
 }

src/codegen/parser.rs

@@ -50,10 +50,8 @@ pub fn parse_single_kernel(raw: &RawKernelConfig) -> Result<KernelConfig> {
                 );
             }
         }
-        SOAC::Histogram => {
-            if raw.bins.is_none() || raw.bins == Some(0) {
-                bail!("Kernel '{}': histogram pattern requires bins > 0", raw.name);
-            }
+        SOAC::Histogram if (raw.bins.is_none() || raw.bins == Some(0)) => {
+            bail!("Kernel '{}': histogram pattern requires bins > 0", raw.name);
         }
         _ => {}
     }

src/manifest/mod.rs

@@ -186,13 +186,11 @@ fn validate_kernel(
                 );
             }
         }
-        SOAC::Histogram => {
-            if kernel.bins.is_none() || kernel.bins == Some(0) {
-                bail!(
-                    "{}: 'histogram' pattern requires a 'bins' field with a positive integer",
-                    ctx
-                );
-            }
+        SOAC::Histogram if (kernel.bins.is_none() || kernel.bins == Some(0)) => {
+            bail!(
+                "{}: 'histogram' pattern requires a 'bins' field with a positive integer",
+                ctx
+            );
         }
         _ => {}
     }
@@ -502,20 +500,44 @@ operator = "+"
 
     #[test]
     fn test_parse_all_backends() {
-        assert_eq!(parse_backend("opencl").expect("TODO: handle error"), GPUBackend::OpenCL);
-        assert_eq!(parse_backend("cuda").expect("TODO: handle error"), GPUBackend::CUDA);
-        assert_eq!(parse_backend("multicore").expect("TODO: handle error"), GPUBackend::Multicore);
-        assert_eq!(parse_backend("c").expect("TODO: handle error"), GPUBackend::C);
+        assert_eq!(
+            parse_backend("opencl").expect("TODO: handle error"),
+            GPUBackend::OpenCL
+        );
+        assert_eq!(
+            parse_backend("cuda").expect("TODO: handle error"),
+            GPUBackend::CUDA
+        );
+        assert_eq!(
+            parse_backend("multicore").expect("TODO: handle error"),
+            GPUBackend::Multicore
+        );
+        assert_eq!(
+            parse_backend("c").expect("TODO: handle error"),
+            GPUBackend::C
+        );
         assert!(parse_backend("vulkan").is_err());
     }
 
     #[test]
     fn test_parse_all_patterns() {
         assert_eq!(parse_pattern("map").expect("TODO: handle error"), SOAC::Map);
-        assert_eq!(parse_pattern("reduce").expect("TODO: handle error"), SOAC::Reduce);
-        assert_eq!(parse_pattern("scan").expect("TODO: handle error"), SOAC::Scan);
-        assert_eq!(parse_pattern("scatter").expect("TODO: handle error"), SOAC::Scatter);
-        assert_eq!(parse_pattern("histogram").expect("TODO: handle error"), SOAC::Histogram);
+        assert_eq!(
+            parse_pattern("reduce").expect("TODO: handle error"),
+            SOAC::Reduce
+        );
+        assert_eq!(
+            parse_pattern("scan").expect("TODO: handle error"),
+            SOAC::Scan
+        );
+        assert_eq!(
+            parse_pattern("scatter").expect("TODO: handle error"),
+            SOAC::Scatter
+        );
+        assert_eq!(
+            parse_pattern("histogram").expect("TODO: handle error"),
+            SOAC::Histogram
+        );
     }
 
     #[test]