fix(connect): relay answers Browser.getVersion locally (stops reconnect storm)

ROOT CAUSE of per-session command drift on the extension path: the daemon's
liveness check (`is_connection_alive` → `Browser.getVersion`) is a BROWSER-level
command. The relay only answered Target.* locally and forwarded the rest, so
Browser.getVersion went to the extension, which can only do per-tab
chrome.debugger → it errored → CdpClient saw TransportError → connection deemed
DEAD → the daemon closed + reconnected + re-ran discover_and_attach_targets on
EVERY command. Each re-discover rebuilds pages from the relay's minimal
targetInfo and resets active_page_index=0, so eval/get-title/screenshot drifted
to the first tab (about:blank / a foreign focused tab).

Reproduced locally (throwaway Chrome + Extensions.loadUnpacked + fork.24 nm-host):
trace showed discover_and_attach_targets running on every command (pages
before=0) and [ev] active_idx reset to 0.

Fix: relay answers Browser.getVersion locally with a stub version (like
getTargets), so the liveness probe succeeds → connection stays alive → no
reconnect/re-discover → the session's active tab is preserved. Pairs with
fork.24's add_background_page. relay.rs: 10 unit tests.

cli/src/native/relay.rs

@@ -107,6 +107,22 @@ impl RelayState {
         let session_id = raw.get("sessionId").and_then(|s| s.as_str());
 
         match method {
+            // Browser-level command the daemon uses as its liveness probe
+            // (`is_connection_alive` → `Browser.getVersion`). The extension only
+            // speaks per-tab `chrome.debugger`, so forwarding it errors → the
+            // daemon would deem the connection dead and reconnect+re-discover on
+            // EVERY command, resetting the active tab (eval/screenshot drift).
+            // Answer it locally so the relay connection reads as alive.
+            "Browser.getVersion" => ClientRoute::Local(json!({
+                "id": id,
+                "result": {
+                    "protocolVersion": "1.3",
+                    "product": "Chrome/ab-connect-relay",
+                    "revision": "",
+                    "userAgent": "",
+                    "jsVersion": ""
+                }
+            })),
             // Discovery is best-effort and event-driven in real CDP; abs only
             // reads the getTargets result, so an empty ack is enough here.
             "Target.setDiscoverTargets" | "Target.setAutoAttach" => {
@@ -302,6 +318,21 @@ mod tests {
         }
     }
 
+    #[test]
+    fn browser_get_version_is_answered_locally() {
+        // Liveness probe must NOT be forwarded (the extension can't do
+        // browser-level commands) — else the daemon reconnects on every command.
+        let mut s = RelayState::new();
+        let route = s.route_client_command(1, &json!({ "id": 7, "method": "Browser.getVersion" }));
+        match route {
+            ClientRoute::Local(v) => {
+                assert_eq!(v["id"], 7);
+                assert!(v["result"]["protocolVersion"].is_string());
+            }
+            _ => panic!("Browser.getVersion must be answered locally"),
+        }
+    }
+
     #[test]
     fn attach_to_target_returns_known_session() {
         let mut s = RelayState::new();