WIP: Batch 2 — backfill tests for fs, shell, and http/workflow

- io/fs.rs: 20 tests (path resolution, project open/close/get, known projects,
  model prefs, file read/write, list dir, validate path, scaffold)
- io/shell.rs: 4 new tests (allowlist, command execution, stdout capture, exit codes)
- http/workflow.rs: 8 tests (parse_test_status, to_test_case, to_review_story)

Coverage: 28.6% → 48.1%

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/io/shell.rs

@@ -106,4 +106,64 @@ mod tests {
             "expected shell execution to be blocked when test plan is not approved"
         );
     }
+
+    #[tokio::test]
+    async fn exec_shell_impl_rejects_disallowed_command() {
+        let dir = tempdir().unwrap();
+        let result = exec_shell_impl(
+            "curl".to_string(),
+            vec!["https://example.com".to_string()],
+            dir.path().to_path_buf(),
+        )
+        .await;
+
+        assert!(result.is_err());
+        assert!(result.unwrap_err().contains("not in the allowlist"));
+    }
+
+    #[tokio::test]
+    async fn exec_shell_impl_runs_allowed_command() {
+        let dir = tempdir().unwrap();
+        let result = exec_shell_impl(
+            "ls".to_string(),
+            Vec::new(),
+            dir.path().to_path_buf(),
+        )
+        .await;
+
+        assert!(result.is_ok());
+        let output = result.unwrap();
+        assert_eq!(output.exit_code, 0);
+    }
+
+    #[tokio::test]
+    async fn exec_shell_impl_captures_stdout() {
+        let dir = tempdir().unwrap();
+        std::fs::write(dir.path().join("hello.txt"), "").unwrap();
+
+        let result = exec_shell_impl(
+            "ls".to_string(),
+            Vec::new(),
+            dir.path().to_path_buf(),
+        )
+        .await
+        .unwrap();
+
+        assert!(result.stdout.contains("hello.txt"));
+    }
+
+    #[tokio::test]
+    async fn exec_shell_impl_returns_nonzero_exit_code() {
+        let dir = tempdir().unwrap();
+        let result = exec_shell_impl(
+            "ls".to_string(),
+            vec!["nonexistent_file_xyz".to_string()],
+            dir.path().to_path_buf(),
+        )
+        .await
+        .unwrap();
+
+        assert_ne!(result.exit_code, 0);
+        assert!(!result.stderr.is_empty());
+    }
 }