refactor: split Claude agent runner entrypoint (#200)

runners/agent-runner/src/compaction-boundary.ts

@@ -0,0 +1,29 @@
+import {
+  compactBoundaryOutput,
+  type RunnerCompaction,
+} from './output-protocol.js';
+
+export function compactBoundaryFromMessage(
+  message: unknown,
+  log: (message: string) => void,
+): RunnerCompaction | undefined {
+  if (
+    !(
+      typeof message === 'object' &&
+      message !== null &&
+      (message as { type?: string }).type === 'system' &&
+      (message as { subtype?: string }).subtype === 'compact_boundary'
+    )
+  ) {
+    return undefined;
+  }
+  const meta = (
+    message as {
+      compact_metadata?: { trigger?: string; pre_tokens?: number };
+    }
+  ).compact_metadata;
+  log(
+    `Compact boundary — trigger=${meta?.trigger || '?'} pre_tokens=${meta?.pre_tokens ?? '?'}`,
+  );
+  return compactBoundaryOutput(meta?.trigger);
+}