refactor(storage): rename dsh-domain to dsh-storage-domain

The bare 'domain' name was too generic for a published package. The
directory moves to packages/storage/storage-domain, the package becomes
@deepseek-ai/dsh-storage-domain, and the plugin/invariant names follow;
the ctx surface (ctx.storage.domain), the domain/changed event, and all
runtime behavior are unchanged. References, catalogs, graphs, and the
bilingual design note move together.

packages/storage/storage-domain/src/spec.ts

@@ -0,0 +1,112 @@
+/**
+ * Domain declaration vocabulary. A spec object is the single source of a
+ * domain's identity, layout, and record schemas: the owning package defines
+ * it once with {@link defineDomain} and both the type surface and the runtime
+ * (validation, descriptor projection) derive from it. Record schemas are zod
+ * (`z.infer` keeps types un-duplicated and the same schemas later project to
+ * RPC wire schemas); plugin `Config` stays schemastery.
+ * @module @deepseek-ai/dsh-storage-domain/src/spec
+ */
+
+import type { ZodType } from 'zod'
+import { UNIT_NAME_RE, type KvUnitDescriptor } from '@deepseek-ai/dsh-storage'
+
+/** Global singleton declaration: schema plus the value used before the first write. */
+export interface DomainGlobalSpec<G> {
+  /** Validates the stored global at the durable boundary. */
+  readonly schema: ZodType<G>
+  /** Value served when the medium holds no global yet; not written until the first `set`. */
+  readonly initial: G
+}
+
+/**
+ * One table declaration. `K` is a phantom key type (typically a branded
+ * string) carried for compile-time projection only; keys are plain strings on
+ * the medium.
+ */
+export interface DomainTableSpec<K extends string = string, V = unknown> {
+  /** Validates every stored record at the durable boundary. */
+  readonly valueSchema: ZodType<V>
+  /** Phantom carrier for the key type; never present at runtime. */
+  readonly __key?: K
+}
+
+/** Static declaration of one domain: identity, version, and record layout. */
+export interface DomainSpec {
+  /** Domain name; must match `UNIT_NAME_RE` (doubles as the backend unit name). */
+  readonly name: string
+  /** Domain format version; a medium stamped with a different version rejects at open. */
+  readonly version: number
+  /** Optional global singleton slot. */
+  readonly global?: DomainGlobalSpec<unknown>
+  /** Table declarations keyed by table name; each name must match `UNIT_NAME_RE`. */
+  readonly tables: Record<string, DomainTableSpec>
+}
+
+/** Key type of one declared table, recovered from its phantom carrier. */
+export type TableKeyOf<S extends DomainSpec, N extends keyof S['tables']> =
+  S['tables'][N] extends DomainTableSpec<infer K> ? K : never
+
+/** Value type of one declared table. */
+export type TableValueOf<S extends DomainSpec, N extends keyof S['tables']> =
+  S['tables'][N] extends DomainTableSpec<string, infer V> ? V : never
+
+/** Global value type of a spec; `never` when the spec declares no global. */
+export type GlobalValueOf<S extends DomainSpec> =
+  S['global'] extends DomainGlobalSpec<infer G> ? G : never
+
+/**
+ * Declare one table.
+ * @param schema - zod schema validating every stored record of this table.
+ * @returns the table declaration, key-typed by `K`.
+ */
+export function domainTable<K extends string, V>(schema: ZodType<V>): DomainTableSpec<K, V> {
+  return { valueSchema: schema }
+}
+
+/**
+ * Identity helper that pins a spec's literal types and validates its shape.
+ * Misconfiguration fails loud at the owning package's module load, before any
+ * medium is touched: a domain or table name outside `UNIT_NAME_RE`, a version
+ * that is not a non-negative integer, or a global schema that accepts `null`
+ * all throw. The `null` rejection guards round-tripping: backends store the
+ * global as opaque JSON with `null` as the "never written" sentinel, so a
+ * nullable global would be indistinguishable from an absent one on reopen
+ * (a stored `null` silently reverts to `initial`).
+ * @param spec - The domain declaration.
+ * @returns the same spec, narrowed to its literal type.
+ */
+export function defineDomain<S extends DomainSpec>(spec: S): S {
+  if (!UNIT_NAME_RE.test(spec.name)) {
+    throw new Error(`domain name '${spec.name}' must match ${UNIT_NAME_RE}`)
+  }
+  if (!Number.isInteger(spec.version) || spec.version < 0) {
+    throw new Error(`domain '${spec.name}' version must be a non-negative integer, got ${spec.version}`)
+  }
+  for (const table of Object.keys(spec.tables)) {
+    if (!UNIT_NAME_RE.test(table)) {
+      throw new Error(`domain '${spec.name}' table name '${table}' must match ${UNIT_NAME_RE}`)
+    }
+  }
+  if (spec.global !== undefined && spec.global.schema.safeParse(null).success) {
+    throw new Error(
+      `domain '${spec.name}' global schema must not accept null: `
+      + 'null is the medium\'s "never written" sentinel, so a stored null could not round-trip',
+    )
+  }
+  return spec
+}
+
+/**
+ * Project a spec onto the backend-facing unit descriptor.
+ * @param spec - The domain declaration.
+ * @returns the descriptor handed to `KvFacet.open`.
+ */
+export function descriptorOf(spec: DomainSpec): KvUnitDescriptor {
+  return {
+    name: spec.name,
+    version: spec.version,
+    tables: Object.keys(spec.tables),
+    hasGlobal: spec.global !== undefined,
+  }
+}