fix(hooks): swallow async EPIPE on hook-stdin write

Hooks whose command exits before reading stdin emit EPIPE on the
async 'error' event — outside the sync try/catch — which node
escalates to an unhandled stream error. Vitest counts that as a
suite failure in CI even when every assertion passes. Adding a
no-op error listener absorbs it.

Author: halfaipg

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "codebase-cli",
-	"version": "2.0.0-pre.63",
+	"version": "2.0.0-pre.64",
 	"description": "Codebase CLI — a TypeScript coding agent on the pi-mono runtime. OAuth-aware, any LLM provider, single install.",
 	"keywords": [
 		"ai",

src/hooks/runner.ts

@@ -60,6 +60,11 @@ export function runHook(config: HookConfig, context: HookEventContext, signal?:
 		};
 		signal?.addEventListener("abort", onAbort);
 
+		// EPIPE is async (emitted on stdin's 'error' event) when the child
+		// exits before consuming our payload — a sync try/catch misses it
+		// and node treats unhandled-stream-error as a process exception.
+		// Swallow the stream error explicitly; close-on-fast-exit is fine.
+		child.stdin?.on("error", () => {});
 		try {
 			child.stdin?.write(JSON.stringify(context));
 			child.stdin?.end();