Add comprehensive tests for PDU.Encoder (87 tests)
Improve coverage from 43.82% to 75.84% with tests for:
- Message encoding (SNMPv1, v2c, v3 delegation)
- PDU encoding (all PDU types: get, getnext, response, set, getbulk)
- Varbind encoding (explicit types, auto types, all SNMP value types)
- Integer encoding edge cases (zero, small, large, negative)
- Counter32/Gauge32/Timeticks (min/max values)
- Counter64 (0 to 18446744073709551615)
- String encoding (empty, short, long, special chars, binary)
- OID encoding (simple, large subids, very large subids, long OIDs)
- Bulk request encoding (non_repeaters, max_repetitions)
- Exception values (no_such_object, no_such_instance, end_of_mib_view)
- Length encoding edge cases (short, medium, long form)
- Error handling (invalid formats, missing fields)
- Complete integration tests (GET/GETNEXT/SET/GETBULK)
Coverage: 1,304 → 1,391 tests, all passing
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
mayor
14ec708e93