feat(context): volunteer-shaped resolve IPC — channel/cwd/volunteer fields, handler-result widening, server-side gate + validated source + delivery-point logging; listener on both engines

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/context/resolve-ipc.test.ts

@@ -7,6 +7,7 @@ import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 import {
   resolveSocketPath,
+  resolveSocketPathForConfig,
   startResolveIpcServer,
   resolveViaIpc,
   resolveViaIpcRaw,