feat(telnet): add port forwarding and shell integration

- Add SLIRP port forwarding: localhost:2323 -> guest:2323
- Add telnetd and pty_test to shell's program registry
- Enables running telnetd from the shell

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

Author: ryanbreen

src/bin/qemu-uefi.rs

@@ -291,11 +291,13 @@ fn main() {
         _ => {
             // Default: SLIRP user-mode networking
             // Traffic is internal to QEMU, not visible on host interfaces
+            // Port forwarding: host:2323 -> guest:2323 (telnet)
             qemu.args([
-                "-netdev", "user,id=net0",
+                "-netdev", "user,id=net0,hostfwd=tcp::2323-:2323",
                 "-device", "e1000,netdev=net0,mac=52:54:00:12:34:56",
             ]);
             eprintln!("[qemu-uefi] Network: SLIRP user-mode (10.0.2.x internal)");
+            eprintln!("[qemu-uefi]   Port forward: localhost:2323 -> guest:2323 (telnet)");
         }
     }
 

userspace/tests/init_shell.rs

@@ -577,6 +577,17 @@ static PROGRAM_REGISTRY: &[ProgramEntry] = &[
         binary_name: b"tcp_client_test\0",
         description: "Send TCP message to 10.0.2.2:18888",
     },
+    ProgramEntry {
+        name: "telnetd",
+        binary_name: b"telnetd\0",
+        description: "Telnet server on port 2323",
+    },
+    // === PTY Test ===
+    ProgramEntry {
+        name: "pty_test",
+        binary_name: b"pty_test\0",
+        description: "Test PTY functionality",
+    },
 ];
 
 /// Find a program in the registry by command name.