fix: use custom viewport dimensions in streaming frame metadata and image resolution (#1033)

* fix: use custom viewport dimensions in streaming frame metadata

  CDP's Page.screencastFrame metadata returns physical device dimensions
  instead of the emulated viewport, causing frame messages to report
  incorrect deviceWidth/deviceHeight when a custom viewport is set.

  Use the viewport dimensions captured at screencast start instead of
  the CDP metadata values, since the screencast image is already captured
  at the configured viewport size.

  Closes #1031

* fix: resize browser content area on viewport change for correct
  screencast dimensions

  Emulation.setDeviceMetricsOverride only changes the CSS viewport, but
  screencast captures the actual browser content area. This caused frame
  images to have incorrect dimensions (e.g., 1000x451 instead of
  1000x1000)
  when a custom viewport was set.

  - Call Browser.setContentsSize after setDeviceMetricsOverride so the
    content area matches the emulated viewport
  - Restart active screencast when viewport dimensions change so
    maxWidth/maxHeight parameters are updated
  - Skip redundant screencast restarts when dimensions are unchanged
  - Extend E2E test to verify actual JPEG image dimensions, not just
    metadata

* fix: pass viewport dimensions to --window-size at launch and log setContentsSize failures

- Add viewport_size to LaunchOptions so --window-size matches the
  configured viewport from the start, reducing reliance on the
  experimental Browser.setContentsSize CDP call at runtime
- Log Browser.setContentsSize failures instead of silently ignoring
  them with let _ =

* fix: remove duplicate viewport change detection block (dead code from merge)

* fix: use log::debug! instead of eprintln! for setContentsSize failure

* revert: use eprintln! instead of log crate for setContentsSize failure

The daemon's stderr pipe is closed after startup, so log crate
subscribers cannot output during normal operation. eprintln! is
visible during startup and in tests, matching the existing convention.

---------

Co-authored-by: hyunjinee <leehj0110@kakao.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cli/src/native/cdp/chrome.rs

@@ -103,6 +103,9 @@ pub struct LaunchOptions {
     pub ignore_https_errors: bool,
     pub color_scheme: Option<String>,
     pub download_path: Option<String>,
+    /// Initial viewport dimensions used for `--window-size` so the content
+    /// area matches the desired viewport from the start.
+    pub viewport_size: Option<(u32, u32)>,
     /// When true, omit `--password-store=basic` and `--use-mock-keychain` so
     /// Chrome uses the real system keychain. Set automatically when launching
     /// with a copied Chrome profile.
@@ -127,6 +130,7 @@ impl Default for LaunchOptions {
             ignore_https_errors: false,
             color_scheme: None,
             download_path: None,
+            viewport_size: None,
             use_real_keychain: false,
         }
     }
@@ -222,7 +226,8 @@ fn build_chrome_args(options: &LaunchOptions) -> Result<ChromeArgs, String> {
         .any(|a| a.starts_with("--start-maximized") || a.starts_with("--window-size="));
 
     if !has_window_size && options.headless && !has_extensions {
-        args.push("--window-size=1280,720".to_string());
+        let (w, h) = options.viewport_size.unwrap_or((1280, 720));
+        args.push(format!("--window-size={},{}", w, h));
     }
 
     args.extend(options.args.iter().cloned());