Improve command logging and log_err module paths (#39674)

Prior we only logged the crate in `log_err`, which is not too helpful.
We now assemble the module path from the file system path.

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/context_server/src/transport/stdio_transport.rs

@@ -41,12 +41,9 @@ impl StdioTransport {
             command.current_dir(working_directory);
         }
 
-        let mut server = command.spawn().with_context(|| {
-            format!(
-                "failed to spawn command. (path={:?}, args={:?})",
-                binary.executable, &binary.args
-            )
-        })?;
+        let mut server = command
+            .spawn()
+            .with_context(|| format!("failed to spawn command {command:?})",))?;
 
         let stdin = server.stdin.take().unwrap();
         let stdout = server.stdout.take().unwrap();