fix(common): restore output helpers after end_quiet_mode

After end_quiet_mode closes fd 3/4, the overridden warn/error/info
functions still reference >&3, causing "bad file descriptor" errors
for any calls after quiet mode ends (e.g. the reboot prompt).
Restore the original function definitions when leaving quiet mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/common.sh

@@ -65,6 +65,15 @@ end_quiet_mode() {
   exec 1>&3 2>&4
   exec 3>&- 4>&-
   echo ""
+
+  # Restore original output helpers (fd 3/4 are closed now)
+  info() { echo -e "${GREEN}[✓]${NC} $1"; }
+  warn() { echo -e "${YELLOW}[!]${NC} $1"; }
+  error() {
+    echo -e "${RED}[✗]${NC} $1"
+    exit 1
+  }
+  step() { echo -e "\n${GREEN}━━━ $1 ━━━${NC}"; }
 }
 
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