fix: allow empty generic tag filter values

[kanishka0411]

Description

Generic tag filters should be able to match empty tag values like {"#d":[""]}. The matcher/query path already treats empty tag values as normal values, but validation rejected them before matching.

This relaxes generic tag filter validation while keeping ids/authors validation unchanged, and adds schema/runtime coverage.

Related Issue

Fixes #259

Motivation and Context

The schema rejects {"#d":[""]} with invalid: "[2].#d[0]" is not allowed to be empty, but the matcher and query path already accept empty tag values. Real events with ["d", ""] exist on the network (NIP-23, NIP-58 badges) and other relays accept this filter. This aligns validation with existing behavior.

How Has This Been Tested?

• pnpm exec mocha test/unit/schemas/filter-schema.spec.ts test/unit/utils/event.spec.ts test/unit/repositories/event-repository.spec.ts
• pnpm build:check
• pnpm exec biome lint src/schemas/filter-schema.ts test/unit/schemas/filter-schema.spec.ts test/unit/utils/event.spec.ts test/unit/repositories/event-repository.spec.ts

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: 1d8c124

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: 63.509%. remained the same — kanishka0411:fix/empty-generic-tag-values into cameri:main