feat(runtime): add CLI streaming process handle

Author: loong10k

src/main/java/io/github/easy4j/opencode/cli/OpenCodeCliStreamHandle.java

@@ -0,0 +1,73 @@
+package io.github.easy4j.opencode.cli;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * Handle for an asynchronously streaming OpenCode CLI child process.
+ *
+ * @author <a href="https://github.com/loong10k">Loong Wan</a>
+ * @since 3.0.0
+ */
+public final class OpenCodeCliStreamHandle {
+
+    private final Process process;
+    private final CompletableFuture<OpenCodeCliResult> completion;
+    private final AtomicBoolean cancellationRequested = new AtomicBoolean();
+
+    OpenCodeCliStreamHandle(Process process, CompletableFuture<OpenCodeCliResult> completion) {
+        this.process = process;
+        this.completion = completion;
+    }
+
+    public CompletableFuture<OpenCodeCliResult> getCompletion() {
+        return completion;
+    }
+
+    public boolean isRunning() {
+        return process != null && process.isAlive() && !completion.isDone();
+    }
+
+    /**
+     * Cancel the local child process tree. This does not call the OpenCode HTTP
+     * session abort endpoint.
+     *
+     * @return true when cancellation was requested before completion
+     */
+    public boolean cancel() {
+        if (completion.isDone()) {
+            return false;
+        }
+        cancellationRequested.set(true);
+        terminateProcessTree();
+        return true;
+    }
+
+    public boolean isCancellationRequested() {
+        return cancellationRequested.get();
+    }
+
+    private void terminateProcessTree() {
+        if (process == null) {
+            return;
+        }
+        ProcessHandle handle = process.toHandle();
+        handle.descendants().forEach(child -> {
+            try {
+                child.destroy();
+            } catch (RuntimeException ignored) {
+            }
+        });
+        process.destroy();
+
+        if (process.isAlive()) {
+            handle.descendants().forEach(child -> {
+                try {
+                    child.destroyForcibly();
+                } catch (RuntimeException ignored) {
+                }
+            });
+            process.destroyForcibly();
+        }
+    }
+}