refactor(nothooks): make hook runner language-agnostic

Remove hardcoded nu interpreter. HookSpec gains an optional interpreter
field; runner infers from file extension (.sh, .nu, .py, .rb, .zsh,
.bash) when not set. Integration tests now use sh — no nu runtime dep
on CI.

crates/nothooks/src/runner.rs

@@ -4,6 +4,28 @@ use notcore::{HookPhase, HookSpec};
 use std::path::PathBuf;
 use std::process::Command;
 
+fn resolve_interpreter(spec: &HookSpec) -> Result<String, String> {
+    if let Some(interp) = &spec.interpreter {
+        return Ok(interp.clone());
+    }
+    let ext = std::path::Path::new(&spec.script)
+        .extension()
+        .and_then(|e| e.to_str())
+        .unwrap_or("");
+    match ext {
+        "nu" => Ok("nu".into()),
+        "sh" => Ok("sh".into()),
+        "bash" => Ok("bash".into()),
+        "zsh" => Ok("zsh".into()),
+        "py" => Ok("python3".into()),
+        "rb" => Ok("ruby".into()),
+        _ => Err(format!(
+            "cannot infer interpreter: no interpreter set and unknown extension {:?}",
+            ext
+        )),
+    }
+}
+
 pub struct HookRunner {
     state_dir: PathBuf,
     force: bool,
@@ -31,8 +53,11 @@ impl HookRunner {
             return HookResult::Skipped;
         }
 
-        // TODO: support other shells
-        let result = Command::new("nu").arg(&spec.script).status();
+        let interp = match resolve_interpreter(spec) {
+            Ok(i) => i,
+            Err(msg) => return HookResult::Failed(msg),
+        };
+        let result = Command::new(&interp).arg(&spec.script).status();
 
         match result {
             Ok(status) if status.success() => {

crates/nothooks/tests/integration.rs

@@ -4,19 +4,20 @@ use std::fs;
 use tempfile::TempDir;
 
 fn make_hook_script(dir: &TempDir, name: &str, content: &str) -> HookSpec {
-    let path = dir.path().join(format!("{name}.nu"));
+    let path = dir.path().join(format!("{name}.sh"));
     fs::write(&path, content).unwrap();
     HookSpec {
         name: name.to_string(),
         script: path.to_str().unwrap().to_string(),
         phase: HookPhase::Dot,
+        interpreter: None,
     }
 }
 
 #[test]
 fn test_hook_success() {
     let dir = TempDir::new().unwrap();
-    let spec = make_hook_script(&dir, "ok-hook", "print hello");
+    let spec = make_hook_script(&dir, "ok-hook", "echo hello");
     let runner = HookRunner::new(dir.path().to_path_buf());
     let result = runner.run_hook(&spec);
     assert!(matches!(result, HookResult::Ok));
@@ -25,7 +26,7 @@ fn test_hook_success() {
 #[test]
 fn test_hook_failure() {
     let dir = TempDir::new().unwrap();
-    let spec = make_hook_script(&dir, "fail-hook", "exit 1\n");
+    let spec = make_hook_script(&dir, "fail-hook", "exit 1");
     let runner = HookRunner::new(dir.path().to_path_buf());
     let result = runner.run_hook(&spec);
     assert!(matches!(result, HookResult::Failed(_)));
@@ -34,7 +35,7 @@ fn test_hook_failure() {
 #[test]
 fn test_setup_hook_skipped_on_rerun() {
     let dir = TempDir::new().unwrap();
-    let mut spec = make_hook_script(&dir, "setup-hook", "print ran");
+    let mut spec = make_hook_script(&dir, "setup-hook", "echo ran");
     spec.phase = notcore::HookPhase::Setup;
 
     let runner = HookRunner::new(dir.path().to_path_buf());
@@ -49,7 +50,7 @@ fn test_setup_hook_skipped_on_rerun() {
 #[test]
 fn test_setup_hook_force_reruns() {
     let dir = TempDir::new().unwrap();
-    let mut spec = make_hook_script(&dir, "force-hook", "print ran");
+    let mut spec = make_hook_script(&dir, "force-hook", "echo ran");
     spec.phase = notcore::HookPhase::Setup;
 
     let runner = HookRunner::new(dir.path().to_path_buf());