chore: remove the data-layer packages (orm/schema/adapters)

[suleimansh]

Removes the four data-layer packages from this repo: @gemstack/orm, @gemstack/orm-memory, @gemstack/orm-drizzle, @gemstack/schema.

Why

These were a frozen spike copy (PR #65) staged for the planned graduation to @gemstack/*. That graduation is cancelled per #66: the universal engines are infrastructure (not user-facing), so they stay @universal-orm, outside the GemStack umbrella. GemStack remains the user-facing brand (AI family + MCP).

vike-data / @universal-orm is the single source of truth for these engines, so the gemstack copies only add fork and accidental-publish risk with no upside.

Safe to remove

• All four are private: true and unpublished.
• Zero dependents anywhere in this repo; zero docs references on main.
• Lockfile pruned; pnpm install --frozen-lockfile passes.

Related

• [orm #1] Decision: brand-consolidation with the Vike team (gate for #64) #66 (closed) decision
• [orm #7] Docs: move ORM from candidate to shipped #72 / PR docs: add the data family (orm + schema + adapters) [#72, HOLD until publish + #66] #73 (closed) docs are moot
• [orm #2] Publish @universal-orm/core + universal-schema (core, together) #67 / [orm #3] Publish @universal-orm/memory + @universal-orm/drizzle (adapters) #68 re-scoped to publish under @universal-orm