feat: one-liner installer + setup install ping

- install.sh: curl-pipe-bash installer with prereq checks (git, bun),
  upgrade detection (git pull if already installed), transparency note
  about update-check pings
- setup: add install ping at end (gstack-update-check --force) to
  register day-zero installs in Supabase
- Install ping only in setup (not install.sh) to avoid double-counting
  (Codex review fix #7)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

install.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+# gstack installer — curl-pipe-bash one-liner
+#
+# Usage:
+#   bash <(curl -fsSL https://raw.githubusercontent.com/garrytan/gstack/main/install.sh)
+#
+set -euo pipefail
+
+INSTALL_DIR="$HOME/.claude/skills/gstack"
+
+echo "gstack installer"
+echo "━━━━━━━━━━━━━━━━"
+echo ""
+
+# ─── Check prereqs ────────────────────────────────────────────
+for cmd in git bun; do
+  if ! command -v "$cmd" >/dev/null 2>&1; then
+    echo "Error: $cmd is required but not found."
+    case "$cmd" in
+      git) echo "  Install: https://git-scm.com/downloads" ;;
+      bun) echo "  Install: curl -fsSL https://bun.sh/install | bash" ;;
+    esac
+    exit 1
+  fi
+done
+
+# Claude CLI check (warn, don't fail — they might install it after)
+if ! command -v claude >/dev/null 2>&1; then
+  echo "Warning: Claude CLI not found."
+  echo "  Install: npm install -g @anthropic-ai/claude-code"
+  echo "  (gstack requires Claude Code to run skills)"
+  echo ""
+fi
+
+# ─── Fresh install vs upgrade ─────────────────────────────────
+if [ -d "$INSTALL_DIR/.git" ]; then
+  echo "gstack already installed — upgrading..."
+  cd "$INSTALL_DIR" && git pull origin main && ./setup
+else
+  echo "Installing gstack to $INSTALL_DIR..."
+  mkdir -p "$(dirname "$INSTALL_DIR")"
+  git clone https://github.com/garrytan/gstack.git "$INSTALL_DIR"
+  cd "$INSTALL_DIR" && ./setup
+fi
+
+echo ""
+echo "Note: gstack checks for updates by pinging our server with your"
+echo "version number, OS, and a random device ID. No usage data is sent."
+echo ""
+echo "gstack installed! Try: /office-hours"

setup

@@ -434,3 +434,10 @@ if [ ! -d "$HOME/.gstack" ]; then
   echo "  Welcome! Run /gstack-upgrade anytime to stay current."
 fi
 rm -f /tmp/gstack-latest-version
+
+# 9. Install ping (best-effort, non-blocking)
+# Fires update-check with --force to register this install in Supabase.
+# Sends only: version, OS, random UUID. No usage data.
+if [ -x "$SOURCE_GSTACK_DIR/bin/gstack-update-check" ]; then
+  "$SOURCE_GSTACK_DIR/bin/gstack-update-check" --force 2>/dev/null &
+fi