fix: keep failed resume side-effect free

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Co-authored-by: Gajae Code <dev@gajae-code.com>

rust/crates/rusty-claude-cli/tests/resume_slash_commands.rs

@@ -222,6 +222,73 @@ fn resume_latest_restores_the_most_recent_managed_session() {
     assert!(stdout.contains(newer_path.to_str().expect("utf8 path")));
 }
 
+#[test]
+fn resume_latest_missing_session_fails_without_creating_session_dirs_435() {
+    // given
+    let temp_dir = unique_temp_dir("resume-latest-missing-435");
+    let project_dir = temp_dir.join("project");
+    let config_home = temp_dir.join("config-home");
+    let home = temp_dir.join("home");
+    fs::create_dir_all(&project_dir).expect("project dir should exist");
+    fs::create_dir_all(&config_home).expect("config home should exist");
+    fs::create_dir_all(&home).expect("home should exist");
+    let envs = [
+        (
+            "CLAW_CONFIG_HOME",
+            config_home.to_str().expect("utf8 config home"),
+        ),
+        ("HOME", home.to_str().expect("utf8 home")),
+        ("ANTHROPIC_API_KEY", ""),
+        ("ANTHROPIC_AUTH_TOKEN", ""),
+        ("OPENAI_API_KEY", ""),
+    ];
+
+    // when — both text and JSON resume failures should be non-zero and read-only.
+    let text = run_claw_with_env(&project_dir, &["--resume", "latest"], &envs);
+    let json = run_claw_with_env(
+        &project_dir,
+        &["--output-format", "json", "--resume", "latest"],
+        &envs,
+    );
+
+    // then
+    assert_eq!(
+        text.status.code(),
+        Some(1),
+        "text resume failure must be non-zero"
+    );
+    assert!(
+        text.stdout.is_empty(),
+        "text resume failure should not claim success on stdout: {}",
+        String::from_utf8_lossy(&text.stdout)
+    );
+    let text_stderr = String::from_utf8_lossy(&text.stderr);
+    assert!(
+        text_stderr.contains("no managed sessions found"),
+        "text failure should explain missing sessions: {text_stderr}"
+    );
+
+    assert_eq!(
+        json.status.code(),
+        Some(1),
+        "JSON resume failure must be non-zero"
+    );
+    assert!(
+        json.stderr.is_empty(),
+        "JSON resume failure should keep stderr empty: {}",
+        String::from_utf8_lossy(&json.stderr)
+    );
+    let parsed: Value = serde_json::from_slice(&json.stdout)
+        .expect("JSON resume failure should emit JSON to stdout");
+    assert_eq!(parsed["status"], "error");
+    assert_eq!(parsed["action"], "restore");
+    assert_eq!(parsed["error_kind"], "no_managed_sessions");
+    assert!(
+        !project_dir.join(".claw").exists(),
+        "failed resume must not create .claw/session directories"
+    );
+}
+
 #[test]
 fn resumed_status_command_emits_structured_json_when_requested() {
     // given