fix(connect): liveness probe + wait @ref support

Two changes that pair with each other:

1. connect_auto_with_fresh_tab now does a Runtime.evaluate "1"
   round-trip after creating the fresh tab. This catches the zombie
   CDP socket case (process alive, websocket dead) where every step
   up to that point reports success but the next user command would
   silently no-op against a dead session. Failing here lets the
   caller surface a proper "CDP session unresponsive" error instead
   of returning Ok and letting `agent-browser open URL` exit 0 with
   a still-blank tab.

2. handle_wait now recognizes @ref selectors (e.g. `wait @e8 --gone`).
   It polls resolve_element_object_id, which already runs the
   verify_ref_identity check from 007fd1b — so:
     - `wait @e8`             succeeds while the original element is
                              still mounted with its snapshot role+name
     - `wait @e8 --gone`      succeeds when the ref's identity changes
                              (modal closed, button re-textified, etc.)
   This gives users the "assert modal still open" primitive that
   prior versions could only approximate with screenshots.

cli/src/native/actions.rs

@@ -1510,6 +1510,28 @@ async fn connect_auto_with_fresh_tab() -> Result<BrowserManager, String> {
         .client
         .send_command("Page.bringToFront", None, Some(&session_id))
         .await;
+
+    // Liveness probe: confirm the CDP session can actually round-trip
+    // before returning success. Without this, a zombie CDP socket (process
+    // alive, websocket dead) would let `connect_auto` and `tab_new` succeed,
+    // we'd return Ok, the next user command would silently no-op, and
+    // `agent-browser open URL` would exit 0 with the browser still on
+    // about:blank. Failing here lets the caller surface the real error.
+    if let Err(e) = mgr
+        .client
+        .send_command("Runtime.evaluate", Some(serde_json::json!({
+            "expression": "1",
+            "returnByValue": true,
+        })), Some(&session_id))
+        .await
+    {
+        return Err(format!(
+            "CDP session is unresponsive after attaching ({}). \
+             The browser may have lost its DevTools connection. \
+             Try: agent-browser close, then re-run.",
+            e
+        ));
+    }
     Ok(mgr)
 }
 
@@ -3105,6 +3127,15 @@ async fn handle_wait(cmd: &Value, state: &mut DaemonState) -> Result<Value, Stri
             .get("state")
             .and_then(|v| v.as_str())
             .unwrap_or("visible");
+        // @-ref support: if the selector is `@e12` style, poll the ref map +
+        // accessibility tree instead of `document.querySelector`. This makes
+        // `wait @e8 --gone` a usable "assert modal still mounted" primitive
+        // for SPA flows where the only stable identity is the AX role+name
+        // captured at snapshot time.
+        if selector.starts_with('@') {
+            wait_for_ref(state, selector, state_str, timeout_ms).await?;
+            return Ok(json!({ "waited": "ref", "ref": selector, "state": state_str }));
+        }
         wait_for_selector(&mgr.client, &session_id, selector, state_str, timeout_ms).await?;
         return Ok(json!({ "waited": "selector", "selector": selector }));
     }
@@ -3316,6 +3347,49 @@ async fn handle_reload(state: &mut DaemonState) -> Result<Value, String> {
 // Wait helpers
 // ---------------------------------------------------------------------------
 
+/// Poll-based wait for a ref-identified element. Resolves the @-ref by
+/// re-running the ref-identity verification each iteration. The supported
+/// states mirror selector-based waits:
+///
+///   - "visible" / "attached" — succeed when the ref resolves to a node
+///     whose AX role + name still match the snapshot entry
+///   - "detached" / "hidden" — succeed when the ref no longer matches
+///     (node removed OR re-textified to something else)
+///
+/// Times out with a "ref X did not become {state}" error.
+async fn wait_for_ref(
+    state: &mut DaemonState,
+    ref_selector: &str,
+    desired_state: &str,
+    timeout_ms: u64,
+) -> Result<(), String> {
+    let want_present = !matches!(desired_state, "detached" | "hidden");
+    let deadline = std::time::Instant::now() + std::time::Duration::from_millis(timeout_ms);
+    loop {
+        let mgr = state.browser.as_ref().ok_or("Browser not launched")?;
+        let session_id = mgr.active_session_id()?.to_string();
+        let resolved = super::element::resolve_element_object_id(
+            &mgr.client,
+            &session_id,
+            &state.ref_map,
+            ref_selector,
+            &state.iframe_sessions,
+        )
+        .await;
+        let present = resolved.is_ok();
+        if present == want_present {
+            return Ok(());
+        }
+        if std::time::Instant::now() >= deadline {
+            return Err(format!(
+                "Timeout: ref {} did not become {} within {}ms",
+                ref_selector, desired_state, timeout_ms
+            ));
+        }
+        tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;
+    }
+}
+
 async fn wait_for_selector(
     client: &super::cdp::client::CdpClient,
     session_id: &str,