feat: add bounded agent compact memory

[christopherjnelson]

Summary

• add one process-local compact memory ledger per agent, capped at eight canonical self-authored entries
• issue deterministic agent-and-tick memory IDs with bounded text and authoritative creation/revision attribution
• add keep, remember, revise, and forget to the existing single-inference flat contract and advance attribution to text-flat-json-v8
• validate memory independently with stable capacity/not-found outcomes and frozen pre-tick, atomic commit semantics
• preserve compatible snapshot, turn, schema-v10 export, and archive behavior while exposing read-only memory inspection in World Lab
• document the contract in ADR 0019 while deferring semantic/vector retrieval, relationships, shared memory, restart persistence, scheduling, and extra inference

Validation

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