PHLEGM v6 opcode-count and classification contract

- Current chipset descriptor contract requires valid_opcode_count, illegal_opcode_count, undocumented_opcode_count, and opcode_count.
- Every individual opcode row independently declares exactly one classification: valid, illegal, or undocumented. Classification is never inferred.
- The loader rejects missing, duplicated, misspelled, unknown, or inconsistent opcode classifications and rejects descriptor/category totals that do not match the loaded rows.
- SELFTEST-QUICK and SELFTEST derive category counts from loaded opcode rows and validate them against the descriptor before execution.
- MOS-6502/MOS-6510/RP2A03: 151 valid + 12 illegal + 93 undocumented = 256 total.
- 8080/8080A: 244 valid + 0 illegal + 12 undocumented = 256 total; 8085: 246 valid + 0 illegal + 10 undocumented = 256 total.
- Z80/Z80A: 698 valid + 0 illegal + 748 undocumented = 1446 total.
- No fallback classification, inference rule, or compatibility alias is retained.
