falcode: fix spawn error handlers (crash fix) + real oc-notify.sh notifier

- falcode.ts: add child.on('error') handlers so a missing notify binary
  (e.g. /bin/true on NixOS) can no longer take down pi via uncaughtException
- scripts/oc-notify.sh: real notifier (notify-send + ntfy) replacing the no-op
- oc-notify.sh also deployed to ~/.local/state/falcode-zellij/ on all machines

scripts/oc-notify.sh

@@ -0,0 +1,55 @@
+#!/bin/sh
+# falcode agent-completion notifier.
+#
+# Spawned by the falcode pi extension (falcode.ts -> fireNotification) when an
+# agent's turn finishes (working -> waiting_user_input) with:
+#   --agent <pi|opencode> --pane-name <cwd-basename> --status idle
+#   --session <zellij-session> --pane-id <n>
+#
+# Sends a desktop popup (notify-send) and an ntfy push so Sam knows the agent
+# finished. Must never exit non-zero in a way that could disturb the caller.
+
+agent=""
+pane_name=""
+status=""
+session=""
+pane_id=""
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --agent) agent="$2"; shift 2 ;;
+    --pane-name) pane_name="$2"; shift 2 ;;
+    --status) status="$2"; shift 2 ;;
+    --session) session="$2"; shift 2 ;;
+    --pane-id) pane_id="$2"; shift 2 ;;
+    *) shift ;;
+  esac
+done
+
+# Only notify on agent-finish transitions.
+[ "$status" = "idle" ] || exit 0
+
+[ -z "$pane_name" ] && pane_name="$agent"
+[ -z "$pane_name" ] && pane_name="pi"
+
+title="✓ $pane_name finished"
+body="$agent agent done"
+[ -n "$session" ] && body="$body · $session"
+
+# 1) Desktop popup
+if command -v notify-send >/dev/null 2>&1; then
+  notify-send -a "Pi" "$title" "$body" >/dev/null 2>&1 || true
+fi
+
+# 2) ntfy push (phone/desktop clients). PI_NTFY_TOPIC comes from
+#    ~/.config/environment.d/10-secrets.conf; fall back to the lab topic.
+topic="${PI_NTFY_TOPIC:-http://192.168.20.35:8099/PI_NTFY_TOPIC}"
+if command -v curl >/dev/null 2>&1; then
+  curl -s -o /dev/null \
+    -H "Title: $title" \
+    -H "Tags: white_check_mark" \
+    -d "$body" \
+    "$topic" >/dev/null 2>&1 || true
+fi
+
+exit 0