chore(drive): close out prisma-next-data-contract

[wmadden-electric]

Closes out the Prisma Next data contract project (Linear: "Prisma App: Prisma Next Data Contract"; slices: #44, #46; TML-3009/3011/3013 Done).

DoD verification

1. Live typed round trip — met: pn-widgets example deploys to Prisma Cloud and round-trips through the PN typed client (E2E job green on feat(app-cloud): deploy migrate lowering for pnPostgres + pn-widgets example (slice 2) #46).
2. Migrate-on-change + no-op redeploy — met: prisma-next-migrate.integration.test.ts ('re-run at the same ref → noop'; 'fresh DB + ref with invariants → migrate; re-run no-ops').
3. No authored path → deploy fails, DB untouched — met: same file ('marker at a different hash with no authored path → fails, DB unchanged').
4. Marker-mismatch warn-and-serve — amended by ADR-0022: schema correctness is deploy-time-only; hydrate does no runtime marker check (test: 'hydrate does no schema verification').
5. Bare postgres() untouched and green — met: storefront-auth E2E green throughout.
6. ADR-0022 merged; deferred design preserved — met: multi-contract/contract-space extension recorded in ADR-0022 §Alternatives (space id on the declaration, never topology-derived).

Final retro (lessons landed durably)

• FT-5226 gotcha now points at the CI cold-connect canary that guards workaround removal (gotchas.md).
• CI-refactor lesson (composite actions must carry script-consumed env vars) and the CONFLICTING-PR-stops-workflows trap landed in operator memory.

Migration & cleanup

• Long-lived content already lives in docs/design (ADR-0022, amended ADR-0015/0017) — nothing to migrate.
• Deferred items (multi-contract pickup prerequisite, dev-time sketch, factory rename) carried to .drive/deferred.md.
• External-reference scan: clean. Transient .drive/projects/prisma-next-data-contract/ deleted.

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