fix(build): include browser.rs clear_viewport/via_relay (#47) + cargo fmt

v1.5.24 (d5cd9cd) shipped a commands.rs caller of `clear_viewport` but not the
browser.rs method it lives in (a concurrent in-progress #47 viewport/resize edit
was only partly staged), so main didn't compile and the format check failed.
Commit the matching browser.rs method + via_relay() helper and run cargo fmt.
Full tree builds; 863 tests pass.

cli/src/commands.rs

@@ -3162,15 +3162,21 @@ fn parse_mouse(rest: &[&str], id: &str) -> Result<Value, ParseError> {
 ///   viewport <width>x<height>        (e.g. 1280x800)
 ///   viewport reset | clear           (drop the override, restore real size)
 fn parse_viewport(rest: &[&str], id: &str) -> Result<Value, ParseError> {
-    const USAGE: &str =
-        "viewport <width> <height> [scale] [--dpr N] [--mobile] | viewport reset";
+    const USAGE: &str = "viewport <width> <height> [scale] [--dpr N] [--mobile] | viewport reset";
 
-    if matches!(rest.first().copied(), Some("reset") | Some("clear") | Some("off")) {
+    if matches!(
+        rest.first().copied(),
+        Some("reset") | Some("clear") | Some("off")
+    ) {
         return Ok(json!({ "id": id, "action": "viewport", "reset": true }));
     }
 
     // Positional (non-flag) tokens. A `WxH` token counts as one positional.
-    let positionals: Vec<&str> = rest.iter().copied().filter(|a| !a.starts_with("--")).collect();
+    let positionals: Vec<&str> = rest
+        .iter()
+        .copied()
+        .filter(|a| !a.starts_with("--"))
+        .collect();
 
     let (w, h, scale_tok): (i32, i32, Option<&str>) = match positionals.first() {
         Some(first) if first.contains('x') || first.contains('X') => {
@@ -3188,9 +3194,10 @@ fn parse_viewport(rest: &[&str], id: &str) -> Result<Value, ParseError> {
             }
         }
         Some(w_str) => {
-            let h_str = positionals
-                .get(1)
-                .ok_or(ParseError::MissingArguments { context: "viewport".to_string(), usage: USAGE })?;
+            let h_str = positionals.get(1).ok_or(ParseError::MissingArguments {
+                context: "viewport".to_string(),
+                usage: USAGE,
+            })?;
             let w = w_str.parse::<i32>().map_err(|_| ParseError::InvalidValue {
                 message: format!("Invalid width: {}", w_str),
                 usage: USAGE,
@@ -3220,13 +3227,12 @@ fn parse_viewport(rest: &[&str], id: &str) -> Result<Value, ParseError> {
         None => None,
     };
     if let Some(i) = rest.iter().position(|a| *a == "--dpr" || *a == "--scale") {
-        let v = rest
-            .get(i + 1)
-            .and_then(|s| s.parse::<f64>().ok())
-            .ok_or(ParseError::InvalidValue {
+        let v = rest.get(i + 1).and_then(|s| s.parse::<f64>().ok()).ok_or(
+            ParseError::InvalidValue {
                 message: "--dpr/--scale needs a number".to_string(),
                 usage: USAGE,
-            })?;
+            },
+        )?;
         scale = Some(v);
     }
     if let Some(s) = scale {
@@ -5442,7 +5448,8 @@ mod tests {
 
     #[test]
     fn test_viewport_dpr_and_mobile_flags() {
-        let cmd = parse_command(&args("viewport 375 812 --dpr 3 --mobile"), &default_flags()).unwrap();
+        let cmd =
+            parse_command(&args("viewport 375 812 --dpr 3 --mobile"), &default_flags()).unwrap();
         assert_eq!(cmd["action"], "viewport");
         assert_eq!(cmd["width"], 375);
         assert_eq!(cmd["height"], 812);

cli/src/native/browser.rs

@@ -1950,9 +1950,17 @@ impl BrowserManager {
     /// CDP browser the endpoint is strict, so we must NOT send the custom param —
     /// hence `None` there. We detect the relay by matching our `ws_url` against
     /// the live relay URL the native-messaging host published.
+    /// Whether this manager is driving the user's real Chrome through the
+    /// `ab-connect` extension relay (vs. a browser we launched or a direct CDP
+    /// endpoint). Detected by matching our `ws_url` against the live relay URL
+    /// the native-messaging host published. Used to avoid relay-unsafe CDP that
+    /// would disturb the user's window (e.g. Browser.setContentsSize, issue #47).
+    fn via_relay(&self) -> bool {
+        crate::connect::relay_url().as_deref() == Some(self.ws_url.as_str())
+    }
+
     fn agent_group(&self) -> Option<String> {
-        let via_relay = crate::connect::relay_url().as_deref() == Some(self.ws_url.as_str());
-        if !via_relay {
+        if !self.via_relay() {
             return None;
         }
         let name = DAEMON_SESSION
@@ -2161,7 +2169,13 @@ impl BrowserManager {
             .await?;
 
         // Screencast captures the actual content area, not the emulated CSS
-        // viewport, so resize the content area to match.
+        // viewport, so resize the content area to match — but ONLY for a browser
+        // we launched. Over the ab-connect relay the "window" is the user's real
+        // Chrome window, and Browser.setContentsSize would physically resize it
+        // (issue #47) — the exact thing the CDP device-metrics override exists to
+        // avoid. The Emulation override above already gives the tab the requested
+        // CSS viewport without touching the OS window, so skip the resize there.
+        if !self.via_relay() {
             if let Ok(target_id) = self.active_target_id() {
                 if let Ok(window_info) = self
                     .client
@@ -2191,10 +2205,27 @@ impl BrowserManager {
                     }
                 }
             }
+        }
 
         Ok(())
     }
 
+    /// Clear the CDP device-metrics override (`viewport reset`), restoring the
+    /// tab's real layout viewport. Never touches the OS window, so it is safe on
+    /// the relay (we never physically resized the user's window — see
+    /// `set_viewport`).
+    pub async fn clear_viewport(&self) -> Result<(), String> {
+        let session_id = self.active_session_id()?;
+        self.client
+            .send_command(
+                "Emulation.clearDeviceMetricsOverride",
+                Some(json!({})),
+                Some(session_id),
+            )
+            .await?;
+        Ok(())
+    }
+
     pub async fn set_user_agent(&self, user_agent: &str) -> Result<(), String> {
         let session_id = self.active_session_id()?;
         self.client