feat: merge adapters-internal into adapters package

[prosdev]

Summary

This PR merges the @lytics/playwright-adapters-internal package into @lytics/playwright-adapters, consolidating all storage adapters into a single package.

Changes

• ✅ Moved FirestoreAdapter from adapters-internal to adapters package
• ✅ Added @google-cloud/firestore dependency to adapters package
• ✅ Added ./firestore subpath export to adapters package.json
• ✅ Updated all documentation to reference adapters instead of adapters-internal
• ✅ Removed adapters-internal package directory
• ✅ Updated config files (tsconfig.json, vitest.config.ts)
• ✅ Added changeset for breaking change
• ✅ All tests passing (128 tests)

Benefits

• One less package to maintain - Reduces overhead
• Simpler dependency management - All adapters in one place
• Better discoverability - Users find FirestoreAdapter alongside other adapters
• Still organized - Subpath exports (/firestore, /filesystem, /slack) maintain clean API

Migration

Before:

import { FirestoreAdapter } from '@lytics/playwright-adapters-internal/firestore';

After:

import { FirestoreAdapter } from '@lytics/playwright-adapters/firestore';

Breaking Change

⚠️ @lytics/playwright-adapters-internal package is removed. Use @lytics/playwright-adapters/firestore instead.

Testing

• ✅ All tests pass (128 tests)
• ✅ Build succeeds
• ✅ Type checking passes