test: add comprehensive tests for PDU.Constants and MIB.Logger
Added complete test coverage for two low-coverage modules:
**PDU.Constants (11.65% -> target 100%)**:
- Error status code accessors and conversions
- SNMPv3 constants (USM security model, max message size)
- PDU type constants and tag conversion (get, getnext, response, set, getbulk)
- Data type constants and tag conversion (all SNMP types)
- SNMP version normalization (:v1, :v2c, :v3)
- OID normalization (list and string formats)
- SNMPv3 message flags encoding/decoding
- Default message flags for security levels
- Error status code/atom conversion
- Roundtrip encoding/decoding verification
- 43 new tests
**MIB.Logger (11.11% -> target 100%)**:
- Compilation lifecycle logging (start, success, error, warning, complete)
- Batch compilation logging (start, progress, success, error)
- Parse progress and import resolution logging
- Code generation and tokenization statistics
- Dependency order and performance metrics
- Vendor quirk handling
- Warning logging with context
- Error type extraction and aggregation
- 40 new tests
Total: 83 new tests added
Test count: 1,128 -> 1,211 (all passing)
mayor
82b4dbdf28