fix(cortex-cli): show user-friendly error for invalid --host value

Fixes bounty issue #1559

When running 'cortex acp --host not.valid', the command previously showed a
raw syntax error 'invalid socket address syntax'. This change validates the
host parameter as a valid IP address before attempting to parse it and
provides a clear error message with expected format hint.

Author: factorydroid

cortex-cli/src/acp_cmd.rs

@@ -3,9 +3,9 @@
 //! The ACP protocol enables IDE integration (like Zed) with Cortex.
 //! Supports both stdio and HTTP transports for flexible integration.
 
-use anyhow::Result;
+use anyhow::{Result, bail};
 use clap::Parser;
-use std::net::SocketAddr;
+use std::net::{IpAddr, SocketAddr};
 use std::path::PathBuf;
 
 /// ACP server CLI command.
@@ -76,6 +76,14 @@ impl AcpCli {
 
     /// Run ACP server with HTTP transport.
     async fn run_http_server(&self, config: cortex_engine::Config) -> Result<()> {
+        // Validate host is a valid IP address before attempting to parse
+        if self.host.parse::<IpAddr>().is_err() {
+            bail!(
+                "Invalid host '{}'. Expected a valid IP address (e.g., 127.0.0.1 or 0.0.0.0)",
+                self.host
+            );
+        }
+
         let addr: SocketAddr = format!("{}:{}", self.host, self.port).parse()?;
 
         eprintln!("Starting ACP server on http://{}", addr);