Add Java SDK cookbook with 7 recipes

Add complete Java cookbook matching the pattern of existing .NET, Go,
Node.js, and Python cookbooks. All 7 recipes included:

- Ralph Loop: Autonomous AI task loops with JBang
- Error Handling: try-with-resources, ExecutionException, timeouts
- Multiple Sessions: Parallel sessions with CompletableFuture
- Managing Local Files: AI-powered file organization
- PR Visualization: Interactive PR age charts
- Persisting Sessions: Save/resume with custom IDs
- Accessibility Report: WCAG reports via Playwright MCP

Each recipe includes both markdown documentation and a standalone
JBang-runnable Java file in recipe/.

cookbook/copilot-sdk/java/recipe/RalphLoop.java

@@ -0,0 +1,55 @@
+///usr/bin/env jbang "$0" "$@" ; exit $?
+//DEPS com.github:copilot-sdk-java:0.2.1-java.1
+
+import com.github.copilot.sdk.*;
+import com.github.copilot.sdk.events.*;
+import com.github.copilot.sdk.json.*;
+import java.nio.file.*;
+
+/**
+ * Simple Ralph Loop — reads PROMPT.md and runs it in a fresh session each iteration.
+ *
+ * Usage:
+ *   jbang RalphLoop.java                  # defaults: PROMPT.md, 50 iterations
+ *   jbang RalphLoop.java PROMPT.md 20     # custom prompt file, 20 iterations
+ */
+public class RalphLoop {
+    public static void main(String[] args) throws Exception {
+        String promptFile = args.length > 0 ? args[0] : "PROMPT.md";
+        int maxIterations = args.length > 1 ? Integer.parseInt(args[1]) : 50;
+
+        System.out.printf("Ralph Loop — prompt: %s, max iterations: %d%n", promptFile, maxIterations);
+
+        try (var client = new CopilotClient()) {
+            client.start().get();
+
+            String prompt = Files.readString(Path.of(promptFile));
+
+            for (int i = 1; i <= maxIterations; i++) {
+                System.out.printf("%n=== Iteration %d/%d ===%n", i, maxIterations);
+
+                // Fresh session each iteration — context isolation is the point
+                var session = client.createSession(
+                    new SessionConfig()
+                        .setOnPermissionRequest(PermissionHandler.APPROVE_ALL)
+                        .setModel("gpt-5.1-codex-mini")
+                        .setWorkingDirectory(System.getProperty("user.dir"))
+                ).get();
+
+                // Log tool usage for visibility
+                session.on(ToolExecutionStartEvent.class,
+                    ev -> System.out.printf("  ⚙ %s%n", ev.getData().toolName()));
+
+                try {
+                    session.sendAndWait(new MessageOptions().setPrompt(prompt)).get();
+                } finally {
+                    session.close();
+                }
+
+                System.out.printf("Iteration %d complete.%n", i);
+            }
+        }
+
+        System.out.println("\nAll iterations complete.");
+    }
+}