feat(click): report (and optionally --follow) a tab opened by a click (#24-A)

A click on a target=_blank link / window.open opened a new tab, but the active
tab stayed put, so the post-click snapshot showed the OLD page — looking exactly
like the click failed. On the relay the new tab is discovered only via getTargets
(the relay doesn't push target events to the daemon), so it went unsurfaced.

handle_click now snapshots tracked targets before the click and, after, runs a
lightweight BrowserManager::adopt_newly_opened (one getTargets, attaches only the
new target — far cheaper than a full resync) to detect a freshly-opened tab. It's
reported as openedTab {tabId,url,title} in the response (and a '→ opened new tab
[tN] <url>' hint in text mode). Default keeps focus on the current tab (so
multi-tab flows aren't hijacked, per #7/#8.1); 'click <sel> --follow' switches to
the new tab. Verified live: clicking a _blank link prints
'→ opened new tab [t13] https://example.org/'.

Completes the #24 friction items (B/C/D shipped in 770708b).

cli/src/native/browser.rs

@@ -1279,6 +1279,67 @@ impl BrowserManager {
     /// the active tab is preserved, and re-pinned if it was pruned. Powers a live
     /// `tab list` and adopt-by-targetId so a fresh session can reach a stranded,
     /// still-filled tab without reloading it (issue #21).
+    /// Detect targets that appeared since the `before` set (e.g. a click that
+    /// opened a new tab via a `target=_blank` link or `window.open`), attach +
+    /// track each in the background, and return the first newly-opened page.
+    ///
+    /// Lighter than [`resync_targets`] — one `getTargets` and work only on the
+    /// new targets, no whole-tab url/title refresh — so it's cheap enough to run
+    /// after every click. The new tab is added in the background (never steals
+    /// the active tab, per #7/#8.1); the caller surfaces it so the agent knows a
+    /// tab opened instead of seeing the old page (issue #24-A).
+    pub async fn adopt_newly_opened(&mut self, before: &HashSet<String>) -> Option<PageInfo> {
+        let result: GetTargetsResult = self
+            .client
+            .send_command_typed("Target.getTargets", &json!({}), None)
+            .await
+            .ok()?;
+        let live: Vec<TargetInfo> = result
+            .target_infos
+            .into_iter()
+            .filter(should_track_target)
+            .collect();
+        let mut opened: Option<PageInfo> = None;
+        for target in &live {
+            if before.contains(&target.target_id)
+                || self.pages.iter().any(|p| p.target_id == target.target_id)
+            {
+                continue;
+            }
+            let attach: AttachToTargetResult = match self
+                .client
+                .send_command_typed(
+                    "Target.attachToTarget",
+                    &AttachToTargetParams {
+                        target_id: target.target_id.clone(),
+                        flatten: true,
+                    },
+                    None,
+                )
+                .await
+            {
+                Ok(r) => r,
+                Err(_) => continue,
+            };
+            let tab_id = self.assign_tab_id();
+            let page = PageInfo {
+                tab_id,
+                label: None,
+                target_id: target.target_id.clone(),
+                session_id: attach.session_id.clone(),
+                url: target.url.clone(),
+                title: target.title.clone(),
+                target_type: target.target_type.clone(),
+            };
+            self.add_background_page(page.clone());
+            let _ = self.enable_domains(&attach.session_id).await;
+            if opened.is_none() {
+                opened = Some(page);
+            }
+        }
+        opened
+    }
+
     pub async fn resync_targets(&mut self) -> Result<(), String> {
         self.client
             .send_command_typed::<_, Value>(