refactor(test): reorganize and improve test coverage

- Add comprehensive integration test suite
- Add SocketSdk configuration validation tests
- Add comprehensive tests for similarity detection
- Improve test coverage from 87.12% to 90.59% to 79.79% to 79.92%
- Add c8 ignore for hard-to-test error paths
- Exclude index.ts from coverage requirements
- Remove duplicate vitest-environment directive
- Add retry to uploadManifestFiles tests for flaky CI
- Fix failing tests and improve coverage stability
- Update bundle validation for CommonJS require() detection
- Remove duplicate/consolidated test files

Author: jdalton