feat(state): warehouse-managed table primitive — shared by #755 and #920 (ADR 0005 step 3)

[masukai]

Problem

ADR 0005's implementation ordering table names a step between #756 (object-storage backend, step 2) and both #920 (warehouse state backend, step 4) and #755 (diff-based incremental, step 5): "Warehouse managed-table primitive (shared by 4 and 5)". Both #755 and #920 already reference it explicitly in their own "Related" sections ("shares the warehouse managed-table primitive, ADR 0005's ordering step 3") — but the primitive itself was never split into its own issue. It's implicit infrastructure two issues depend on that nobody can pick up independently, and both are currently stuck behind it in the unscheduled backlog.

Proposal

A shared internal component (not user-facing on its own) that both #755 and #920 build on:

• Create-if-absent DDL for a drt-owned schema/table, on the sources with write access — BigQuery / Snowflake / Databricks / Postgres, the same set tracked mirror (feat(engine): tracked mirror — state-based differential deletes (only delete rows drt itself synced) #686) already established on the destination side
• A pre-created-schema escape hatch (grant only create/delete on a named schema rather than "let drt create schemas") — feat(engine): diff-based incremental — warehouse-side snapshot diff, no cursor column required #755's proposal names this explicitly, matching Hightouch Lightning's documented pattern
• Idempotent / safe against concurrent creators (two syncs' first run racing to create the same managed table)
• Distinct from feat(destinations): managed destination tables — opt-in auto-create + on_schema_change drift policy #760 (managed destination tables): that's user data tables on the destination side; this is drt's own bookkeeping tables on the source side

Scope

In: the primitive itself — DDL generation, idempotent creation, the escape-hatch config knob, across the four warehouse sources above.
Out: the diff computation (#755) and the state backend wiring (#920) that consume it — this issue is purely the shared foundation.

Related

• feat(engine): diff-based incremental — warehouse-side snapshot diff, no cursor column required #755, feat(state): warehouse-backed state backend — SQL-queryable observability (opt-in, requires write grant) #920 — both blocked on this
• feat(engine): tracked mirror — state-based differential deletes (only delete rows drt itself synced) #686 — tracked mirror already proved "state table + SQL diff" on the destination side; this generalizes it to the source side
• ADR 0005 — names this as implementation ordering step 3

Milestone fit

Unscheduled backlog, same as #755/#920 (both cut from v0.9's active scope 2026-08-06 per ROADMAP.md). Pull in when either #755 or #920 gets picked up — this is what unblocks both.