ADR-011: Consolidate core + replay into single `verist` package

Status

Accepted

Problem: @verist/core and @verist/replay were separate packages, but replay depends entirely on core types and is always used together. Consumers had to install and import from two packages for basic workflows.
Why now: Several packages (@verist/batch, @verist/pipeline, @verist/queue, @verist/otel, @verist/artifacts) were speculative and unused. Consolidating now reduces maintenance surface before the first stable release.
Constraints: The merged package must export everything both packages previously exported so dependent packages (@verist/llm, @verist/storage, @verist/storage-pg, @verist/cli) compile with only import path changes.

Chosen option: Merge @verist/core and @verist/replay into a single verist package. Delete unused packages.
Rationale:
- Single import for the primary API (import { defineStep, recompute, diff } from "verist")
- Eliminates circular dependency risk between core and replay
- Removes 5 speculative packages that added maintenance cost with no consumers

Keep separate packages: Higher install/import friction, split API surface for tightly coupled functionality.
Merge into @verist/core: Keeps scoped name but loses the cleaner verist top-level import.

Positive: Single dependency for most consumers; simpler workspace; fewer packages to version/publish.
Negative: Larger single package (though tree-shaking mitigates bundle size).
Follow-ups: Update sandbox project and docs to use verist imports. Re-introduce queue/pipeline packages only when there are real consumers.