Add langchain4j-interop: Spring AI 2.0 and LangChain4j 1.22 side by side

Same order assistant in both frameworks against a local fake OpenAI
server: starter bean collision, wire differences, tool failure and loop
bounds, observability meters, MCP-first tools, and a compile check of
the 2025 article's snippets and Maven coordinates.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01G8ikz8xdWuTP5yun8DZ1hk

langchain4j-interop/src/test/java/com/ankurm/interop/Transcript.java

@@ -0,0 +1,43 @@
+package com.ankurm.interop;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+/** Writes a numbered transcript under {@code output/} and echoes it. Every console block in the article is one of these files. */
+final class Transcript implements AutoCloseable {
+
+    private final Path path;
+    private final StringWriter buffer = new StringWriter();
+    private final PrintWriter out = new PrintWriter(buffer);
+
+    Transcript(String fileName, String title) {
+        this.path = Path.of("output", fileName);
+        out.println("# " + title);
+        out.println();
+    }
+
+    Transcript line(String format, Object... args) {
+        out.println(args.length == 0 ? format : String.format(format, args));
+        return this;
+    }
+
+    Transcript blank() {
+        out.println();
+        return this;
+    }
+
+    @Override
+    public void close() {
+        out.flush();
+        try {
+            Files.createDirectories(path.getParent());
+            Files.writeString(path, buffer.toString());
+        } catch (IOException e) {
+            throw new IllegalStateException("could not write " + path, e);
+        }
+        System.out.print(buffer);
+    }
+}