chore: initialize go-sip repository

scripts/acceptance-local.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+set -eu
+
+root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+cd "$root"
+
+./scripts/check-contracts.sh
+go mod verify
+go test -race ./...
+go vet ./...
+go build -trimpath -buildvcs=false -o dist/sip-go-agent ./cmd/sip-go-agent
+
+tmp=$(mktemp -d)
+trap 'rm -rf "$tmp"' EXIT
+./dist/sip-go-agent agent --mode mock --spool "$tmp/spool" >/dev/null
+./dist/sip-go-agent dispatcher --mode mock --db "$tmp/dispatcher.db" >/dev/null
+
+if ./dist/sip-go-agent dispatcher --mode real --db "$tmp/real.db" >/dev/null 2>&1; then
+    echo "real mode unexpectedly started without broker credentials" >&2
+    exit 1
+fi
+
+echo "local P1 acceptance passed for the current single-node/Cell/tenant scope; external production gates are intentionally deferred to phase two"