Move Vault test client from node-vault to @litehex/node-vault

[cristianrgreco]

Summary

• move the Vault module test client from node-vault to @litehex/node-vault
• migrate Vault integration test usage to Client + kv2.write/read
• update package-lock.json to remove the postman-request/legacy node-vault chain

Why

• upstream issue: node-vault#272
• the critical vulnerabilities in that chain have been open for months, even with a PR fix in place upstream

Verification Commands

• npm run format
• npm run lint
• npm run test -- packages/modules/vault/src/vault-container.test.ts
• npm audit

Test Results

• packages/modules/vault/src/vault-container.test.ts: 2 passed, 0 failed

Semver Impact

• patch
• non-breaking evidence: no public runtime API or exported types changed; only Vault module test dependency and tests were updated

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[cristianrgreco]

Closing as duplicate now that #1263 was updated to be the Vault-only migration PR. AGENTS.md guidance changes are tracked separately in #1265.