diag(connect): log CDP transport mode to detect 'Allow remote debugging?' modal source (#31)

The consent modal only appears on a raw remote-debugging attach or a browser we
launched with a debug port — never on the ab-connect extension relay. Append one
line per connection to ~/.chrome-use/connect-mode.log (relay | raw-port-attach |
launched | remote-ws), flagging 'CONSENT-MODAL-RISK' when a raw-port/launch path
runs while the relay was available. Lets us tell a code regression from Chrome's
own extension-debugger consent UX when the modal reappears. Best-effort, never
fails a connection. Verified: normal 'open' logs mode=relay (consent-free).

cli/src/connect.rs

@@ -449,6 +449,47 @@ pub fn relay_url() -> Option<String> {
     }
 }
 
+/// Append a one-line record of how a CDP connection was established, to
+/// `~/.chrome-use/connect-mode.log`. This is the smoking-gun detector for the
+/// "Allow remote debugging?" consent modal: that modal ONLY appears on a raw
+/// remote-debugging attach / a browser we launched with a debug port — NEVER on
+/// the extension relay. When the modal reappears, this log says which session
+/// took which path and when, so we can tell a code regression (`raw-port` /
+/// `launched` while the relay was up) from Chrome's own extension-debugger
+/// consent UX. Low volume (one line per connection); best-effort, never fails a
+/// connection.
+pub fn log_connect_mode(ws_url: &str, launched: bool, session: &str) {
+    let relay = relay_url();
+    let relay_up = relay.is_some();
+    let mode = if launched {
+        "launched(debug-port)"
+    } else if relay.as_deref() == Some(ws_url) {
+        "relay"
+    } else if ws_url.contains("127.0.0.1") || ws_url.contains("localhost") {
+        "raw-port-attach"
+    } else {
+        "remote-ws"
+    };
+    // A raw-port attach or a self-launch while the relay was available is the
+    // exact thing that pops the consent modal — flag it loudly in the line.
+    let suspect = (mode == "raw-port-attach" || launched) && relay_up;
+    let line = format!(
+        "session={session} mode={mode} relay_up={relay_up}{} ws={ws_url}\n",
+        if suspect { " CONSENT-MODAL-RISK" } else { "" }
+    );
+    if let Some(home) = dirs::home_dir() {
+        let path = home.join(".chrome-use").join("connect-mode.log");
+        use std::io::Write;
+        if let Ok(mut f) = std::fs::OpenOptions::new()
+            .create(true)
+            .append(true)
+            .open(&path)
+        {
+            let _ = f.write_all(line.as_bytes());
+        }
+    }
+}
+
 /// Sidecar recording the connected extension's version, written by the host when
 /// it receives the extension's `hello` (sibling of `relay-cdp-url`). Lets
 /// `doctor` surface which extension build is live without a CDP round-trip.

cli/src/native/browser.rs

@@ -490,6 +490,13 @@ impl BrowserManager {
             }
         };
 
+        // A launched browser carries a debug port → it's the other path that can
+        // pop Chrome's consent modal; record it for #31 diagnosis.
+        crate::connect::log_connect_mode(
+            &ws_url,
+            true,
+            DAEMON_SESSION.get().map(String::as_str).unwrap_or("default"),
+        );
         let manager = if engine == "lightpanda" {
             initialize_lightpanda_manager(ws_url, process).await?
         } else {
@@ -585,6 +592,13 @@ impl BrowserManager {
         headers: Option<Vec<(String, String)>>,
     ) -> Result<Self, String> {
         let ws_url = resolve_cdp_url(url).await?;
+        // Record the transport so a reappearing "Allow remote debugging?" modal
+        // can be traced to a raw-port attach vs the consent-free relay (#31).
+        crate::connect::log_connect_mode(
+            &ws_url,
+            false,
+            DAEMON_SESSION.get().map(String::as_str).unwrap_or("default"),
+        );
         let client = Arc::new(CdpClient::connect_with_headers(&ws_url, headers).await?);
         let mut manager = Self {
             client,