feat: add --version flag to CLI (#94)

Print the current version when `agent-browser --version` is passed.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

cli/src/output.rs

@@ -1197,6 +1197,7 @@ Options:
   --headed                   Show browser window (not headless)
   --cdp <port>               Connect via CDP (Chrome DevTools Protocol)
   --debug                    Debug output
+  --version, -V              Show version
 
 Environment:
   AGENT_BROWSER_SESSION          Session name (default: "default")
@@ -1215,3 +1216,7 @@ Examples:
 "#
     );
 }
+
+pub fn print_version() {
+    println!("agent-browser {}", env!("CARGO_PKG_VERSION"));
+}