feat: add connect command for persistent CDP sessions (#127)

Adds a `connect <port>` command that establishes a CDP connection
to a running browser. The daemon remembers the connection, so
subsequent commands work without needing --cdp on every call.

Example:
  agent-browser connect 9222
  agent-browser snapshot  # works without --cdp
  agent-browser tab
  agent-browser close

cli/src/commands.rs

@@ -337,6 +337,19 @@ pub fn parse_command(args: &[String], flags: &Flags) -> Result<Value, ParseError
         // === Close ===
         "close" | "quit" | "exit" => Ok(json!({ "id": id, "action": "close" })),
 
+        // === Connect (CDP) ===
+        "connect" => {
+            let port_str = rest.get(0).ok_or_else(|| ParseError::MissingArguments {
+                context: "connect".to_string(),
+                usage: "connect <port>",
+            })?;
+            let port: u16 = port_str.parse().map_err(|_| ParseError::MissingArguments {
+                context: format!("connect: invalid port '{}'", port_str),
+                usage: "connect <port>",
+            })?;
+            Ok(json!({ "id": id, "action": "launch", "cdpPort": port }))
+        }
+
         // === Get ===
         "get" => parse_get(&rest, &id),
 

cli/src/output.rs

@@ -1261,6 +1261,7 @@ Core Commands:
   pdf <path>                 Save as PDF
   snapshot                   Accessibility tree with refs (for AI)
   eval <js>                  Run JavaScript
+  connect <port>             Connect to browser via CDP (e.g., connect 9222)
   close                      Close browser
 
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