Keep poisoned test locks from cascading across unrelated regressions

The repo-local backlog was effectively exhausted, so this sweep promoted the
newly observed test-lock poisoning pain point into ROADMAP #74 and fixed it in
place. Test-only env/cwd lock acquisition now recovers poisoned mutexes in the
remaining strict call sites, and each affected surface has a regression that
proves a panic no longer permanently poisons later tests.

Constraint: Keep the fix test-only and avoid widening runtime behavior changes
Rejected: Refactor shared helper signatures across broader call paths | unnecessary churn beyond the remaining strict test sites
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: These guards only recover the mutex; tests that mutate env or cwd still must restore process-global state explicitly
Tested: cargo fmt --all --check
Tested: cargo clippy --workspace --all-targets -- -D warnings
Tested: cargo test --workspace
Tested: Architect review (APPROVE)
Not-tested: Additional fault-injection around partially restored env/cwd state after panic
Related: ROADMAP #74

rust/crates/commands/src/lib.rs

@@ -4152,6 +4152,24 @@ mod tests {
         LOCK.get_or_init(|| Mutex::new(()))
     }
 
+    fn env_guard() -> std::sync::MutexGuard<'static, ()> {
+        env_lock()
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+    }
+
+    #[test]
+    fn env_guard_recovers_after_poisoning() {
+        let poisoned = std::thread::spawn(|| {
+            let _guard = env_guard();
+            panic!("poison env lock");
+        })
+        .join();
+        assert!(poisoned.is_err(), "poisoning thread should panic");
+
+        let _guard = env_guard();
+    }
+
     fn restore_env_var(key: &str, original: Option<OsString>) {
         match original {
             Some(value) => std::env::set_var(key, value),
@@ -5214,7 +5232,7 @@ mod tests {
 
     #[test]
     fn discovers_omc_skills_from_project_and_user_compatibility_roots() {
-        let _guard = env_lock().lock().expect("env lock");
+        let _guard = env_guard();
         let workspace = temp_dir("skills-omc-workspace");
         let user_home = temp_dir("skills-omc-home");
         let claude_config_dir = temp_dir("skills-omc-claude-config");