PHLEGM v6 per-opcode classification enforcement

Each opcode entry in every current `.phlegm` opcode table is explicitly classified as `valid`, `illegal`, or `undocumented`.

Enforcement:
- LoadOpcodeFile requires the classification as the sixth metadata field before the first semicolon.
- Only valid / illegal / undocumented are accepted.
- Missing, extra, duplicated, or unknown classification metadata fails definition loading.
- OpcodeDef retains the classification in classCode.
- Primary and secondary indexes must agree on classification for the same opcode key.
- Chipset descriptor valid/illegal/undocumented/total counts are required and are checked against counts derived from the loaded rows.
- SELFTEST-QUICK and SELFTEST validate the row-derived class counts.
- Repository validation scans every opcodes*.config.phlegm table, including Z80 auxiliary prefixed indexes.

No classification is inferred from opcode values, mnemonics, semantics, or historical aliases.
