test: add NIP-04 integration coverage for encrypted direct messages

[Priyanshubhartistm]

Description

Adds integration test coverage for NIP-04 Encrypted Direct Messages (kind 4).

What was added

• New feature file:
  • test/integration/features/nip-04/nip-04.feature
• New step definitions:
  • test/integration/features/nip-04/nip-04.feature.ts

Covered scenarios

1. Alice publishes a kind 4 event with Bob’s pubkey in p tag (accepted/stored).
2. Alice retrieves her sent DM by event ID.
3. Bob subscribes using #p filter with his pubkey and receives Alice’s DM.
4. Charlie subscribed to the same #p filter receives the same ciphertext payload (relay forwards as-is).
5. Duplicate submission of the same kind 4 event returns duplicate: command result.

Notes

• Reused existing integration framework patterns (Cucumber/Gherkin + shared helpers).
• Added deterministic handling for duplicate command-result assertion to avoid replay/race issues.
• No relay/business logic was modified; this is test-only coverage.

Related Issue

Closes
#506

Motivation and Context

NIP-04 is listed as supported by the relay but had no integration test coverage.
This PR closes that gap and verifies the expected relay behavior for kind 4 DM storage, querying, tag-based subscription, and duplicate handling.

How Has This Been Tested?

• npm run docker:integration:run -- npm run test:integration -- test/integration/features/nip-04/nip-04.feature
  • Result: 34 scenarios (34 passed), 200 steps (200 passed)
• Commit hooks also ran successfully:
  • npm run lint
  • npm run build:check
  • npm run test:unit (489 passing)

Screenshots (if appropriate):

N/A

Types of changes

• Non-functional change (docs, style, minor refactor)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my code changes.
• I added a changeset, or this is docs-only and I added an empty changeset.
• All new and existing tests passed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 8df5e78

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
nostream	Patch

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[coveralls]

coverage: 74.929%. remained the same — Priyanshubhartistm:test/nip-04-integration-tests into cameri:main