Production error logging to System.out in IpcServer

**Affected version:** HEAD

**File:** `maven-resolver-named-locks-ipc/src/main/java/org/eclipse/aether/named/ipc/IpcServer.java:196`

```java
private static void error(String msg, Throwable t) {
System.out.println("[ipc] [error] " + msg);
t.printStackTrace(System.out);
}
```

All errors in the IPC server go to stdout instead of a proper logging framework (SLF4J). In a production Maven build, these messages are invisible or interleaved with build output. Same issue for `debug()` (line 184) and `info()` (line 190) in the same file.

Originally reported in #1944.

Start in maven-resolver-named-locks-ipc/src/main/java/org/eclipse/aether/named/ipc/IpcServer.java, focusing on debug() at line 184, info() at line 190, and error() at line 196. Replace the System.out and stack-trace output with SLF4J logging, then verify that all IPC server messages use the proper logging framework instead of standard output.

Written by the indexing model from the issue text.