fix: handle stdin error in ponytail-mode-tracker to avoid uncaught crash (#147) (#227)

Without a stdin 'error' listener, a broken pipe or parent-process crash
causes Node to emit an unhandled error event on the stream, which becomes
an uncaught exception and crashes the hook with a non-zero exit code.

Add process.stdin.on('error', () => process.exit(0)) before the data/end
listeners. Exiting 0 on error keeps the hook contract: always exit cleanly,
never block session start.

Fixes #147

hooks/ponytail-mode-tracker.js

@@ -6,6 +6,7 @@ const { getDefaultMode, isDeactivationCommand } = require('./ponytail-config');
 const { clearMode, setMode, writeHookOutput } = require('./ponytail-runtime');
 
 let input = '';
+process.stdin.on('error', () => process.exit(0)); // broken pipe / parent crash: exit clean, never block session
 process.stdin.on('data', chunk => { input += chunk; });
 process.stdin.on('end', () => {
   try {