feat(ui-slots): bind inject hooks compartments into use<Name> selector hooks

Registrant-private reactive facts previously reached components as raw
observables that each component subscribed by hand (InputBar notices/
lexicon via uSES, SettingsRoot via a version/subscribe/getter triple).
The inject face now carries a reserved hooks compartment of bare
sources; the renderer binds each into a use<Name> selector hook through
the same machinery as the provide channel, so components consume
useNotices/useLexicon/useSections and never see a subscription
primitive. InputBar and SettingsRoot are the first two consumers.

packages/client/ui-conversation/src/client/apply.ts

@@ -135,13 +135,15 @@ export function apply(ctx: Context): void {
       'conversation.input.model': { kind: 'single', scope: 'session' },
     },
     inject: (sessionId: SessionId): ComposerBarInjected => {
+      const shell = inputHub.shell(sessionId)
       return {
-        keyboard: inputHub.keyboard(sessionId),
+        keyboard: shell,
         stop: () => {
           scopedConversation(sessions, sessionId).cancel().catch(() => {
             // Stop failure surfaces via snapshot.promptError; nothing to restore.
           })
         },
+        hooks: { notices: shell.notices, lexicon: shell.lexicon },
       }
     },
   }, InputBar)

packages/client/ui-conversation/src/client/contract/slots.ts

@@ -1,11 +1,11 @@
 /** Conversation slot declarations and their composed component props. */
 import type { ReactNode, RefObject } from 'react'
 import type {
-  MaybeSnapshotSelectorHook, PropsRenderSlots, PropsRuntime, PropsStore, SnapshotSelectorHook,
+  InjectFace, MaybeSnapshotSelectorHook, PropsRenderSlots, PropsRuntime, PropsStore, SnapshotSelectorHook,
 } from '@deepseek-ai/dsh-client-ui-slots'
-import type { ConversationSnapshot, PendingInteraction, SessionId, ToolCallBlock, WorkspaceId } from '@deepseek-ai/dsh-client-runtime/client'
+import type { ConversationSnapshot, ObservableSnapshot, PendingInteraction, SessionId, ToolCallBlock, WorkspaceId } from '@deepseek-ai/dsh-client-runtime/client'
 import type {} from '@deepseek-ai/dsh-client-ui-layout/client'
-import type { ComposerKeyboard, InputActions, InputState } from '../input/contract.ts'
+import type { ComposerKeyboard, InputActions, InputNotice, InputState } from '../input/contract.ts'
 import type { createChatStore } from '../stores.ts'
 import type { CallId, SelectionTarget, ViewTab } from './views.ts'
 
@@ -220,6 +220,13 @@ export interface ComposerBarInjected {
   keyboard: ComposerKeyboard
   /** Cancel the in-flight turn. */
   stop: () => void
+  /** Registrant hooks compartment: the renderer binds these to useNotices/useLexicon. */
+  hooks: {
+    /** Latest surfaced notice (null after none; seq keys re-render of repeats). */
+    notices: ObservableSnapshot<InputNotice | null>
+    /** Hot plain-text reference lexicon for the decoration scan (decision 21). */
+    lexicon: ObservableSnapshot<ReadonlyMap<'/' | '@', readonly string[]>>
+  }
 }
 
 /**
@@ -231,11 +238,11 @@ export interface InputControlOwnerProps {
   locked: boolean
 }
 
-/** Full composer-bar component props: standard kit & owner share & control-seat render share & injected share. */
+/** Full composer-bar component props: standard kit & owner share & control-seat render share & injected share (hooks compartment bound). */
 export type ComposerBarProps =
   PropsRuntime<'conversation.composer.bar'>
   & PropsRenderSlots<'conversation.input.plan' | 'conversation.input.model'>
-  & ComposerBarInjected
+  & InjectFace<ComposerBarInjected>
 
 /**
  * Composer chain currency: what ConversationRoot dispatches at its

packages/client/ui-conversation/src/client/input/contract.ts

@@ -5,7 +5,7 @@
  * conversation wiring layer alone sees the full SessionInput. InputMachine
  * (machine.ts) is package-private and never exported.
  */
-import type { ClientContext, ObservableSnapshot, SnapshotStore } from '@deepseek-ai/dsh-client-runtime/client'
+import type { ClientContext, SnapshotStore } from '@deepseek-ai/dsh-client-runtime/client'
 import type {
   ArbitrateKey, ArbitrateOutcome, CommandClaim, ConsumeTokenRequest, PickOutcome,
   ReferenceInsert, SubmitOutcome, TokenSpan,
@@ -77,8 +77,6 @@ export interface InputNotice {
  * satisfies it structurally.
  */
 export interface ComposerKeyboard {
-  /** Latest surfaced notice store (null after none). */
-  readonly notices: SnapshotStore<InputNotice | null>
   /** Live machine state for event-handler reads (render reads go through useInput). */
   readonly snapshot: InputState
   /** Draft write with the DOM-observed edit shape (narrows occurrence math). */
@@ -99,8 +97,6 @@ export interface ComposerKeyboard {
   space(): boolean
   /** Dismiss the popupSelect shell (any interaction outside the box). */
   dismissPopup(): void
-  /** Hot plain-text reference lexicon source for the decoration scan (decision 21; empty Map without a pipeline). */
-  readonly lexicon: ObservableSnapshot<ReadonlyMap<'/' | '@', readonly string[]>>
 }
 
 /** One queued-message row projected from the session/queued frames (T9 supplies the store). */

packages/client/ui-conversation/src/client/skeleton/InputBar.tsx

@@ -1,11 +1,12 @@
 /** The default composer body: the 'conversation.composer.bar' slot entry
  * (decision 20). Machine state arrives through the standard provide channel
  * (useInput + inputActions); the keyboard/DOM command face and stop arrive
- * through this entry's own inject; layout-phase inputs (variant, placeholder,
+ * through this entry's own inject, whose hooks compartment binds
+ * useNotices/useLexicon; layout-phase inputs (variant, placeholder,
  * region-slot content) ride the owner props. Session facts
  * (running/removed/promptError) are self-selected via useSession. */
 
-import { useEffect, useRef, useState, useSyncExternalStore } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import type { ChangeEvent, KeyboardEvent, MouseEvent, ReactNode } from 'react'
 import clsx from 'clsx'
 import { IconPlusOutline16 } from '@deepseek-ai/dsh-client-ui-primitives'
@@ -27,20 +28,12 @@ const READONLY_OPTIONS: readonly { id: string; label: string }[] = [
 ]
 
 export function InputBar({
-  useSession, useInput, inputActions, keyboard, stop, renderSlot,
+  useSession, useInput, inputActions, keyboard, stop, renderSlot, useNotices, useLexicon,
   variant, placeholder, accessory, overlay, leftItems, rightItems, onAdd, addLabel = 'Add attachment',
 }: InputBarProps) {
   const input = useInput(s => s)
-  const noticeStore = keyboard.notices
-  const notice = useSyncExternalStore(
-    (fn: () => void) => noticeStore.subscribe(fn),
-    () => noticeStore.getSnapshot(),
-  )
-  const lexiconStore = keyboard.lexicon
-  const lexicon = useSyncExternalStore(
-    (fn: () => void) => lexiconStore.subscribe(fn),
-    () => lexiconStore.getSnapshot(),
-  )
+  const notice = useNotices(s => s)
+  const lexicon = useLexicon(s => s)
   const promptError = useSession(s => s.promptError)
   const running = useSession(s => s.running)
   const disabled = useSession(s => s.removed)