fix(claude-code): remove the erroring attention-bell hook

The hook rang the terminal bell by walking the process ancestry for a
process named `claude`, but nix wraps the binary so its `comm` is
`.claude-wrapped`.
The match never fired: the bell never rang, and the loop fell through to
a non-zero exit that surfaced as a Stop hook error on every turn.

Remove the hook, its script, and the Stop and Notification wiring.
The tmux monitor-bell config is left in place as a general nicety.

modules/claude-code/claude-code.nix

@@ -10,18 +10,6 @@
 let
   cfg = config.modules.claude-code;
   user = config.user.name;
-
-  # Rings the terminal bell so tmux flags the background pane.
-  bellHook = [
-    {
-      hooks = [
-        {
-          type = "command";
-          command = "~/.claude/hooks/attention-bell.sh";
-        }
-      ];
-    }
-  ];
 in
 {
   options.modules.claude-code.enable = lib.mkEnableOption ''
@@ -57,14 +45,11 @@ in
         skills = ./skills;
 
         # Installed under ~/.claude/hooks, referenced by the settings below.
-        hooks."attention-bell.sh" = builtins.readFile ./hooks/attention-bell.sh;
         hooks."agent-sudo-guard.sh" = builtins.readFile ./hooks/agent-sudo-guard.sh;
 
         settings = {
           model = "opus";
           hooks = {
-            Stop = bellHook;
-            Notification = bellHook;
             PreToolUse = [
               {
                 matcher = "Bash";

modules/claude-code/hooks/attention-bell.sh

@@ -1,21 +0,0 @@
-#!/bin/sh
-# attention-bell.sh — ring the terminal bell in this Claude session's tmux pane
-# so tmux's monitor-bell flags the (background) window red in the status bar.
-#
-# Claude Code runs hooks as detached subprocesses: they have no controlling
-# terminal, so /dev/tty is unavailable here. But the parent-process chain up to
-# the `claude` process stays intact, and `claude` itself holds the pane's pty.
-# So we walk ancestry to find it and write the bell straight to that tty.
-# (Writing a bare BEL to an explicit /dev/pts/N works even from a detached
-# process — verified against tmux's window_bell_flag.)
-
-pid=$PPID
-while [ "$pid" -gt 1 ] 2>/dev/null; do
-	if [ "$(ps -o comm= -p "$pid" 2>/dev/null)" = claude ]; then
-		tty=$(ps -o tty= -p "$pid" 2>/dev/null | tr -d ' ')
-		[ -n "$tty" ] && [ "$tty" != '?' ] && printf '\a' > "/dev/$tty"
-		exit 0
-	fi
-	pid=$(ps -o ppid= -p "$pid" 2>/dev/null | tr -d ' ')
-	[ -z "$pid" ] && break
-done