ecs: schema-based ArchetypeRowOf/ArchetypeHandleOf for stripInternal services

[krisnye]

Description

Lets a consumer that keeps a hand-written public service interface (not type Service = Database.Plugin.ToDatabase<typeof plugin>) and marks the plugin database type @internal derive its public archetype-handle types so db.archetypes is assignable with no cast — and emit cleanly under stripInternal: true.

Why Database.Archetype.RowOf (#122) doesn't cover this

Database.Archetype.RowOf<S, K> derives from the plugin database type. When that type is @internal (kept small / hides internals), declaration emit breaks two ways:

1. Referenced publicly → TS7056. The emitter serializes typeof plugin into the consumer's .d.ts.
2. @internal → dangling/dropped. TypeScript never resolves a row through a stripped symbol — it preserves the reference, leaving a dangling import type { … } → downstream TS2305.

I verified empirically that no extractor form can force inlining through an @internal symbol (named alias, inline anonymous, and deep-Expand all either dangle or get dropped). The only sound path is to reference a public symbol.

What this adds

ArchetypeSchema / ArchetypeRowOf / ArchetypeHandleOf (in src/ecs/store/archetype-row.ts) resolve an archetype's row from a small public schema ({ components, archetypes }) rather than the plugin database type — the same row as db.archetypes[K], but the emitted type references only public symbols.

import type { ArchetypeHandleOf } from "@adobe/data/ecs";

export const trackComponents = { trackKind: { type: "string" }, muted: { type: "boolean" } } as const;
export const trackSchema = { components: trackComponents, archetypes: { Track: ["trackKind", "muted"] } } as const;

// plugin built from trackSchema may stay @internal
export interface TrackService {
  readonly archetypes: { readonly Track: ArchetypeHandleOf<typeof trackSchema, "Track"> };
}

db.archetypes.Track (from the @internal db) assigns to TrackService["archetypes"]["Track"] with no cast; downstream resolves Track to its concrete columns.

Acceptance gate

scripts/emit-stripinternal (pnpm check:emit) emits a stripInternal fixture and type-checks a downstream consumer, asserting: no TS7056; the @internal plugin + db type are stripped; the service .d.ts is self-contained (no plugin/@internal reference, small); and rows resolve to exact concrete columns via a mutual-assignability gate (no dangling import).

The README documents the pattern plus the declaration-emit footguns surfaced while building the gate (reference the handle inline; no fenced ```ts blocks with import/export/interface in JSDoc above an exported type; don't let the schema be a module's lone export).

Verification

• tsc -b clean; eslint clean; full suite (2531 tests) green.
• node scripts/emit-stripinternal/check.mjs → PASS (all 9 assertions).

Related PRs

Follows #122 (Database.Archetype.RowOf for derived service types).