cursor: unbounded per-conversation maps leak in long-lived processes

[code-yeongyu]

conversationStateCache / conversationBlobStores / rotatedConversationIds (packages/ai/src/api/cursor-agent.ts:302-311) never evict; blob stores hold per-conversation byte blobs. In a long-lived RPC/multi-session daemon this is a slow leak. Proposal: TTL or LRU cap; verification: drive 1000 distinct conversation ids and assert bounded sizes. (2026-08-20 audit, arch-protocol D6.)