fix(zapier): address review feedback (masked key, ES imports) + test hygiene

- authentication: API key field is now type 'password' so Zapier masks it in
  the connection UI instead of showing it in cleartext.
- index: use ES imports for the platform version and package version instead of
  require(), matching the repo's TypeScript rule. dist stays flat; both versions
  resolve at runtime.
- AGENTS.md: add the Key Directories row for integrations/zapier-mem0.
- tests: disable telemetry during test runs so CI never fires real PostHog
  events, which also removes a lingering open handle after the suite.

Verified: build + zapier validate (0 failures) + 16 tests (13 unit, 3 live E2E).

integrations/zapier-mem0/package.json

@@ -36,6 +36,7 @@
   "jest": {
     "testEnvironment": "node",
     "testMatch": ["**/test/**/*.test.ts"],
+    "setupFiles": ["<rootDir>/test/setup.ts"],
     "transform": {
       "^.+\\.tsx?$": ["ts-jest", {}]
     }