ci(integrations): add CI/CD workflows for n8n + Zapier packages

Match the repo's per-integration CI/CD convention (vercel-ai / pi-agent
pattern):

- n8n-nodes-mem0-checks.yml (lint + build + dist verify) and
  n8n-nodes-mem0-cd.yml (npm publish --provenance via OIDC, dispatched by
  the release router on tag n8n-nodes-mem0-v*).
- zapier-mem0-checks.yml (zapier validate) and zapier-mem0-cd.yml (manual
  zapier push; requires ZAPIER_DEPLOY_KEY). Zapier deploys to Zapier's
  platform, not npm, so it is not in the release router.
- Wire both packages into ci-gate.yml (path filters + call jobs + gate).
- Register the n8n tag prefix in release.yml and document it + the Zapier
  manual-deploy in AGENTS.md.
- Skip the Zapier E2E suite when MEM0_API_KEY is absent so CI is green
  offline (it still runs locally with a key).

.github/workflows/zapier-mem0-checks.yml

@@ -0,0 +1,40 @@
+name: zapier-mem0 checks
+
+# On PRs this is invoked by ci-gate.yml (the single required check);
+# push-to-main and manual runs remain standalone.
+#
+# CI runs `zapier validate` (offline schema + style checks). The end-to-end
+# jest suite is skipped here because it hits the live Mem0 API — it runs
+# locally with MEM0_API_KEY set (see the package README).
+on:
+  workflow_dispatch:
+  push:
+    branches: [main]
+    paths:
+      - 'integrations/zapier-mem0/**'
+      - '.github/workflows/zapier-mem0-checks.yml'
+  workflow_call:
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 9
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: 'pnpm'
+          cache-dependency-path: integrations/zapier-mem0/pnpm-lock.yaml
+
+      - name: Install dependencies
+        run: cd integrations/zapier-mem0 && pnpm install --frozen-lockfile
+
+      - name: Validate Zapier app definition
+        run: cd integrations/zapier-mem0 && npx zapier-platform-cli@19 validate