feat: add team sync infrastructure (config, auth, push/pull, CLI)

- lib/sync-config.ts: reads .gstack-sync.json + ~/.gstack/auth.json
- lib/auth.ts: device auth flow (browser OAuth, local HTTP callback)
- lib/sync.ts: Supabase push/pull via raw fetch(), offline queue, cache
- lib/cli-sync.ts: CLI handler for gstack-sync commands
- bin/gstack-sync: bash wrapper (setup, status, push-*, pull, drain)
- .gstack-sync.json.example: template for team setup

Zero new dependencies — uses raw fetch() against PostgREST API.
All sync is non-fatal with 5s timeout and offline queue fallback.

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

bin/gstack-sync

@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+# gstack-sync — team data sync CLI.
+#
+# Usage:
+#   gstack-sync setup              — interactive auth flow
+#   gstack-sync status             — show sync status (queue, cache, connection)
+#   gstack-sync push-eval <file>   — push an eval result JSON to Supabase
+#   gstack-sync push-retro <file>  — push a retro snapshot JSON
+#   gstack-sync push-qa <file>     — push a QA report JSON
+#   gstack-sync push-ship <file>   — push a ship log JSON
+#   gstack-sync pull               — pull team data to local cache
+#   gstack-sync drain              — drain the offline queue
+#   gstack-sync logout             — clear auth tokens
+#
+# Env overrides (for testing):
+#   GSTACK_DIR          — override auto-detected gstack root
+#   GSTACK_STATE_DIR    — override ~/.gstack state directory
+set -euo pipefail
+
+GSTACK_DIR="${GSTACK_DIR:-$(cd "$(dirname "$0")/.." && pwd)}"
+
+case "${1:-}" in
+  setup)
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" setup
+    ;;
+  status)
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" status
+    ;;
+  push-eval)
+    FILE="${2:?Usage: gstack-sync push-eval <file.json>}"
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" push-eval "$FILE"
+    ;;
+  push-retro)
+    FILE="${2:?Usage: gstack-sync push-retro <file.json>}"
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" push-retro "$FILE"
+    ;;
+  push-qa)
+    FILE="${2:?Usage: gstack-sync push-qa <file.json>}"
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" push-qa "$FILE"
+    ;;
+  push-ship)
+    FILE="${2:?Usage: gstack-sync push-ship <file.json>}"
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" push-ship "$FILE"
+    ;;
+  pull)
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" pull
+    ;;
+  drain)
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" drain
+    ;;
+  logout)
+    exec bun run "$GSTACK_DIR/lib/cli-sync.ts" logout
+    ;;
+  *)
+    echo "Usage: gstack-sync {setup|status|push-eval|push-retro|push-qa|push-ship|pull|drain|logout}"
+    echo ""
+    echo "Commands:"
+    echo "  setup              Interactive auth flow (opens browser)"
+    echo "  status             Show sync status (queue, cache, connection)"
+    echo "  push-eval <file>   Push eval result JSON to team store"
+    echo "  push-retro <file>  Push retro snapshot JSON"
+    echo "  push-qa <file>     Push QA report JSON"
+    echo "  push-ship <file>   Push ship log JSON"
+    echo "  pull               Pull team data to local cache"
+    echo "  drain              Drain the offline sync queue"
+    echo "  logout             Clear auth tokens"
+    exit 1
+    ;;
+esac