fix: add tie-breaker to upsertMany

[Anshumancanrock]

Description

This PR fixes a gap in EventRepository.upsertMany() for replaceable and parameterized-replaceable events.

upsert() already handled the NIP-01 tie-break rule for equal timestamps (lower lexical event_id wins), but upsertMany() only compared strictly newer timestamps. That made batch paths behave differently from single-event ingestion.

Changes in this PR:

• Updated upsertMany() conflict condition to match upsert() semantics:
  • update when excluded.event_created_at is newer
  • OR when timestamps are equal and existing event_id is lexically greater
• Added focused unit coverage for upsertMany():
  • returns 0 for empty input
  • applies NIP-01 tie-break logic in batch conflict updates

Related Issue

Fixes #536

Motivation and Context

Nostr replaceable events require deterministic winners when created_at ties occur. Without this fallback in upsertMany(), import/batch flows could keep a different winner than the live websocket path, which creates inconsistent relay state for the same event set.

This aligns batch behavior with existing single-event behavior and preserves protocol-consistent conflict resolution.

How Has This Been Tested?

• Ran: npm run test:unit -- test/unit/repositories/event-repository.spec.ts
• Verified new upsertMany tests pass:
  • returns 0 when no events are provided
  • applies NIP-01 tie-breaker in batch conflict condition
• Confirmed generated SQL condition includes the equal-timestamp event_id fallback.

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.

[coveralls]

coverage: 74.55% (+0.07%) from 74.483% — fix/batch-tiebreak into main

[Copilot]

Pull request overview

This PR aligns batch replaceable-event ingestion (EventRepository.upsertMany()) with single-event ingestion (upsert()) by applying NIP-01’s deterministic tie-break rule when created_at timestamps are equal.

Changes:

• Update upsertMany()’s conflict-update condition to also update on equal timestamps when the incoming event_id is lexically smaller.
• Add unit tests covering upsertMany([]) === 0 and verifying the generated conflict WHERE condition includes the tie-breaker.
• Add a Changesets entry documenting the patch fix.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/repositories/event-repository.ts	Extends upsertMany()’s ON CONFLICT update condition to match NIP-01 tie-break semantics used by upsert().
test/unit/repositories/event-repository.spec.ts	Adds focused unit coverage for upsertMany() empty input and tie-breaker conflict condition.
.changeset/fix-upsertmany-tiebreak.md	Records the change as a patch release note.

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