test: Phase 4 parallel enhancement - 178 lines, 3 files to 99-100% coverage

Parallel test development using 3 agents simultaneously achieved exceptional results:

Coverage Improvements:
1. protocol_checker.py: 27.27% → **100%** (72 lines, +23 tests)
2. sensor_parsers.py: 26.39% → **99.31%** (70 lines, +11 tests)
3. protocol_loader.py: 53.8% → **100%** (36 lines, +12 tests)

**Total: 178 lines covered, 46 new tests added**

Protocol Checker Enhancements (test_protocol_checker.py):
- TestRecommendationGeneration (7 tests): All recommendation branches
- TestAlertLevelEdgeCases (5 tests): NONE/WARNING/CRITICAL logic
- TestInterventionStatusEdgeCases (5 tests): Completed/pending/overdue
- TestCriterionResultDetails (2 tests): Reasoning and missing params
- TestComplexScenarios (4 tests): Multi-stage workflows

Sensor Parsers Enhancements (test_sensor_parsers.py):
- FHIR edge cases (4 tests): Diastolic BP, missing values, empty arrays
- SimpleJSON edge cases (2 tests): Missing keys, all vital mappings
- Normalize vitals (5 tests): Unknown units, thresholds, comprehensive

Protocol Loader Enhancements (test_protocol_loader.py):
- TestProtocolLoaderEdgeCases (12 tests):
  - Invalid/empty JSON handling
  - Missing required fields (name, version, order, timing, condition)
  - None value handling for escalation_criteria
  - Hidden files in protocol directory
  - Optional fields validation

All 144 tests passing (30→53, 40→51, 28→40).

Phase 4 Progress: 289 total lines (111 trajectory + 178 parallel)
Gap to 70%: 1,260 → 971 lines remaining (22.9% complete)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: GeneAI