Add chronicle subgraph query helpers for common OASIS workflows.

[kayodebristol]

From ROADMAP Phase 1 (ROADMAP.md).

Item:

• Add chronicle subgraph query helpers for common OASIS workflows.

Context:

Phase 1 — Reliability & Streaming

• Streaming diff output to sinks (console/file/WebSocket).
• Harden retention policies and archival targets.
• Add chronicle subgraph query helpers for common OASIS workflows.