feat(ql3): establish 3.0 incubation baseline

back/runtime/compatibility/observeLegacyChildProcess.ts

@@ -0,0 +1,42 @@
+import type { ChildProcess } from 'child_process';
+import type { LegacyExecutionObservation } from '../ports/legacyExecutionObserver';
+
+export interface LegacyProcessObservationOptions {
+  now?: () => number;
+  logArtifactId?: string;
+}
+
+export function observeLegacyChildProcess(
+  child: ChildProcess,
+  observation: LegacyExecutionObservation,
+  options: LegacyProcessObservationOptions = {},
+): void {
+  const now = options.now ?? Date.now;
+  child.once('spawn', () => {
+    const atMs = now();
+    observation.spawned({
+      atMs,
+      ...(child.pid === undefined ? {} : { pid: child.pid }),
+      ...(child.pid === undefined
+        ? {}
+        : { executorHandle: `legacy-local:${child.pid}` }),
+      ...(options.logArtifactId === undefined
+        ? {}
+        : { logArtifactId: options.logArtifactId }),
+    });
+    observation.running({ atMs });
+  });
+  child.on('error', () => {
+    observation.startFailed({
+      atMs: now(),
+      errorCode: 'LEGACY_PROCESS_ERROR',
+    });
+  });
+  child.once('exit', (exitCode, signal) => {
+    observation.exited({
+      atMs: now(),
+      exitCode,
+      ...(signal === null ? {} : { signal }),
+    });
+  });
+}