refactor(gui): move the snapshot-store engine into the client runtime

The data layer no longer depends on the React glue package, and business
plugins no longer depend on web-react at all:

- The store engine (zustand vanilla + immer + persist + dev freeze),
  defineStore, and shallowEqual move to @deepseek-ai/dsh-client-runtime,
  exported from the ./client main entry — no ./store subpath survives on
  either package (the web-react one is deleted, none is opened on runtime).
- Store products are bare snapshot sources: useSelector leaves
  SnapshotStore/StoreInstance and Session; every hook is composed at the
  binding site in web-react's renderer (per-source cached uSES binding).
  The SlotRendererHost sessions face carries bare observables only.
- SessionProvider becomes a standard-kit seat: an entry whose children
  declare a session-scope slot receives the framework component as a prop,
  retiring the last value import of web-react from plugin packages.
  UseSession and the session-area types now live in ui-slots.
- web-react shrinks to the shell-only React glue (renderer, providers,
  uSES bridge); zustand/immer belong to runtime alone; the module-table
  seed and tsdown externals drop the web-react/store seat.
- NODE_ENV replacement is defined once in the shared tsdown client preset
  (browser bundles inline the engine and lost vite's define); the 3-line
  process.env typecheck shim moves to runtime with the engine.
- Stray tsc artifacts (.js/.d.ts/.d.ts.map beside sources under src/)
  swept repo-wide; they shadow real sources under vitest resolution.

Verified: both aggregate typecheck programs at zero; 604 client tests
green; repo-wide grep for web-react/store at zero; real-host playwright
run 7/7 including persist round-trip.

ci: fix test/docs

packages/client/runtime/src/client/index.ts

@@ -12,7 +12,7 @@
 import type { Context } from 'cordis'
 import type { ConnectionHandle, SessionId } from '@deepseek-ai/dsh-client-connection/client'
 import type { SnapshotSelectorHook } from '@deepseek-ai/dsh-client-ui-slots'
-import type { SnapshotStore, UseSession } from '@deepseek-ai/dsh-client-web-react'
+import type { SnapshotStore } from './store/index.ts'
 import { SlotsService } from './slots.ts'
 import { SessionsService } from './sessions/service.ts'
 import type { SessionListState } from './sessions/service.ts'
@@ -25,6 +25,13 @@ export type { RootOwnerProps } from './slots.ts'
 export { SessionsService, scopeOf } from './sessions/service.ts'
 export type { Session } from './sessions/session.ts'
 export type { SessionBinding, SessionListState, SessionSummary } from './sessions/service.ts'
+// The snapshot-store engine lives here since the store migration (the data
+// layer owns its substrate; web-react is React glue only). The './client'
+// main export is the single serving door — no store subpath.
+export { createSnapshotStore, defineStore, shallowEqual } from './store/index.ts'
+export type {
+  EngineStoreHandle, EngineStoreInstance, ObservableSnapshot, SnapshotStore,
+} from './store/index.ts'
 export type {
   AssistantBlock, AssistantMessageNode, ContextMessageNode, ConversationNode, ConversationSnapshot,
   PendingInteraction, RunningToolCall, SteeringMessageNode,
@@ -45,7 +52,7 @@ export type { SessionId } from '@deepseek-ai/dsh-client-connection/client'
 export type ClientContext = Context
 
 /** The conversation-snapshot selector hook (ConvViewProps/ToolViewProps take this). */
-export type UseConversationSession = UseSession<ConversationSnapshot>
+export type UseConversationSession = SnapshotSelectorHook<ConversationSnapshot>
 
 /**
  * One tool call as the chat flow renders it: still-running (spinner card) or