Built-in summary artifact family

[marklubin]

Problem

Summary memory should be a first-class Synix build family rather than a pile of app-specific transforms. It needs checkpoint-scoped synthesis and a standard runtime path back to source evidence.

Scope

In scope:

• checkpoint-scoped summary artifacts
• hierarchical or rollup-style summary composition
• source-backed provenance chains
• runtime exposure through the standard tool API

Out of scope:

• benchmark-specific policy naming
• summary-only systems with no provenance path

Dependencies

• Depends on Built-in chunk artifact family #83
• Depends on Python-local runtime/tool API for snapshot-scoped banks #82

Acceptance Criteria

• Summary artifacts are typed and provenance-complete
• Summary retrieval resolves back to source evidence chains
• Summary builds are checkpoint-scoped and reusable across reruns

Required Automated E2E Test

Build checkpoint-scoped summaries over chunked source data, mount the bank, retrieve summaries through the runtime, and verify each returned ref resolves back to source evidence.

Docs Updates Required

• built-in summary family reference
• provenance chain behavior
• runtime retrieval semantics for summaries

Demo Or Template Follow-On

Record a follow-on update to 01-chatbot-export-synthesis showing the built-in summary family instead of an ad hoc composition path.