Remove temporary planning documents that are no longer needed:
- IMPLEMENTATION_EXACT.md
- IMPLEMENTATION_PLAN.md
- TEST_RELIABILITY_PLAN.md
- baseline-results.txt
- cmd/server/tests/TEST_CLEANUP_PATTERN.md
- cmd/server/tests/TEST_COVERAGE.md
- cmd/server/tests/universal_progress_integration_test.go
These were internal planning documents and temporary test files that have
served their purpose and are now being cleaned up from the repository.