feat: target-ontology-adapter §9 Sanity-check sketches

[deanban]

Hand-authored manifest sketches under docs/target-adapter-sanity-checks/ validating that the protocol surface is sufficient for OMOP, NYC ACRIS, and MSK Databricks shapes without out-of-contract escape hatches.

Tracking: #97. Source: openspec/changes/target-ontology-adapter/tasks.md §9.

Tasks

• 9.1 manifest-omop-sketch.md (curated CDM subset)
• 9.2 manifest-acris-sketch.md (GRAPH_NODE/GRAPH_EDGE with valid_from/valid_to)
• 9.3 manifest-databricks-sketch.md (AGGREGATE obligations + EXTERNAL_SEQUENCE PKs)
• 9.4 Verify each sketch references only in-spec DTOs and protocol methods