fix(aionrs): scope tool call IDs by conversation

[catPaw-s]

Summary

• namespace AionRS tool-call message IDs by conversation
• reject cross-conversation message-ID collisions in the SQLite upsert path
• preserve the original conversation row and recency when a collision is rejected

Problem

Tool-call messages use call_id as the globally unique messages.id. When different conversations receive the same upstream tool-use ID, the previous aionrs-{tool_use_id} mapping lets the later upsert patch the existing row while that row still belongs to the first conversation.

Verification

• just push -u origin codex/fix-aionrs-tool-call-id-scope
  • migration immutability check
  • workspace clippy and formatting checks
  • cargo nextest run --workspace: 7531 passed, 18 skipped
• regression tests cover conversation-scoped AionRS IDs and database rejection of cross-conversation collisions

Observability

Existing tool-call persistence error logging already reports rejected upserts without logging prompts, tool input/output, or other sensitive payloads, so no new logging was added.