Adopt portable KAG index family

[8Dionysus]

Summary

• replace tracked KAG v2 monoliths with the portable v3 manifest and content-addressed JSONL shards
• pin CI to the accepted aoa-kag D-0017 owner implementation
• preserve deterministic v2 compatibility assembly while enforcing tracked-size and generated-delta budgets

Migration evidence

• shards: 743
• tracked bytes: 33249508
• migration delta: 79668573 bytes across 751 generated files
• family digest: 23f28c077642d7b3b710d74265a7354af0e374a0260132b85330745ae3b6edd0
• explicit one-time migration receipt is bound to this digest

Validation

• full-build portable-family fixed point
• incremental portable-family fixed point
• portable-family schema, digest, shard, compatibility, size, and receipt validation
• repository-owned validation lanes