fix: guard final writeHookOutput against stdout EPIPE in ponytail-activate (#149) (#152)

The final writeHookOutput('SessionStart', ...) call was the only operation
in the file outside a try/catch. writeHookOutput ends in a bare
process.stdout.write, so a closed stdout / broken pipe (EPIPE) at hook exit
throws uncaught and crashes the hook with a non-zero exit code. Wrap it to
match the file's existing never-block-session-start posture.

hooks/ponytail-activate.js

@@ -71,4 +71,8 @@ if (!isCodex) try {
   // Silent fail — don't block session start over statusline detection
 }
 
-writeHookOutput('SessionStart', mode, output);
+try {
+  writeHookOutput('SessionStart', mode, output);
+} catch (e) {
+  // Silent fail — stdout closed/EPIPE at hook exit must not surface as a hook failure
+}