feat: add CDP connection support for external browsers (#24)

* feat: add CDP connection support for external browsers

Add --cdp flag to connect to browsers via Chrome DevTools Protocol.
This enables control of Electron apps, Chrome instances, or any browser
exposing a CDP endpoint.

- Add cdpPort option to launch command schema
- Implement connectViaCDP() using chromium.connectOverCDP()
- Track browser connection type for proper reconnection handling
- Collect all pages from all contexts for CDP connections

Usage: agent-browser --cdp 9222 snapshot

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* feat: enhance CDP connection handling and improve page tracking

* main.rs update

Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>

* fix: verify CDP connection is alive before early return in launch()

Prevents misleading errors when the remote browser crashes by checking
isConnected() before reusing an existing browser reference.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: reconnect when CDP port changes instead of reusing existing browser

Ensures --cdp flag is respected even when a browser session already exists.
Adds tests for launch() reconnection behavior.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Update src/browser.ts

Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>

* fix: improve CDP connection handling and validation

* feat: add CDP connection validation to ensure browser context accessibility

* Update src/browser.ts

Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>

* feat: enhance CDP connection handling and add reconnect logic

* fix: improve CDP connection handling during browser closure

* fix: reset cdpPort to null during browser initialization

* feat: enhance browser launch logic to handle CDP connection switching

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>

cli/src/output.rs

@@ -1194,6 +1194,7 @@ Options:
   --json                     JSON output
   --full, -f                 Full page screenshot
   --headed                   Show browser window (not headless)
+  --cdp <port>               Connect via CDP (Chrome DevTools Protocol)
   --debug                    Debug output
 
 Examples:
@@ -1204,6 +1205,7 @@ Examples:
   agent-browser find role button click --name Submit
   agent-browser get text @e1
   agent-browser screenshot --full
+  agent-browser --cdp 9222 snapshot      # Connect via CDP port
 "#
     );
 }