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-settings/tests/apply.spec.ts

@@ -60,22 +60,25 @@ describe('ui-settings apply', () => {
     const b = await bench()
     declare(b.slots)
     await b.ctx.plugin({ inject: [...inject], apply }).await()
-    const injected = injectedOf(b.slots)
+    const { sections } = injectedOf(b.slots).hooks
     // The shell ships no sections of its own — registrants fill the ledger.
-    expect(injected.sections()).toEqual([])
+    expect(sections.getSnapshot()).toEqual([])
     b.slots.register({ name: 'settings.section', id: 'z', order: 20, label: 'Z' } as never, () => null)
     // No order and no label: both projection defaults apply.
     b.slots.register({ name: 'settings.section', id: 'a' } as never, () => null)
-    expect(injected.sections()).toEqual([
+    const rows = sections.getSnapshot()
+    expect(rows).toEqual([
       { id: 'a', order: 0, label: '' },
       { id: 'z', order: 20, label: 'Z' },
     ])
-    expect(injected.sectionsVersion()).toBe(b.slots.getVersion('settings.section'))
+    // Snapshot identity is stable until the ledger moves (uSES contract).
+    expect(sections.getSnapshot()).toBe(rows)
     const listener = vi.fn()
-    const off = injected.subscribeSections(listener)
+    const off = sections.subscribe(listener)
     b.slots.register({ name: 'settings.section', id: 'b', order: 1, label: 'B' } as never, () => null)
     await Promise.resolve()
     expect(listener).toHaveBeenCalled()
+    expect(sections.getSnapshot()).not.toBe(rows)
     off()
   })
 

packages/client/ui-settings/tests/settings-root.spec.tsx

@@ -1,5 +1,6 @@
 // @vitest-environment jsdom
 import { afterEach, describe, expect, it, vi } from 'vitest'
+import { useEffect, useState } from 'react'
 import { act, cleanup, fireEvent, render, screen } from '@testing-library/react'
 import type { SettingsRootComponentProps } from '../src/client/contract/slots.ts'
 import { SettingsRoot } from '../src/client/SettingsRoot.tsx'
@@ -22,9 +23,9 @@ function mount({
     { id: 'models', order: 10, label: 'Models' },
   ],
 }: { wide?: boolean; rows?: Row[] } = {}) {
-  // Mutable row store standing in for the ledger; bump() plays a change.
+  // Mutable row source standing in for the bound useSections hook; bump()
+  // plays a ledger change through the same observable contract.
   let current = rows
-  let version = 0
   const listeners = new Set<() => void>()
   const renderSlot = vi.fn(
     ((key: string, _owner: unknown, opts?: { only?: string }) => {
@@ -38,19 +39,21 @@ function mount({
     useSessions: unusedHook,
     useWorkspaces: unusedHook,
     wide,
-    sectionsVersion: () => version,
-    subscribeSections: (listener) => {
-      listeners.add(listener)
-      return () => { listeners.delete(listener) }
+    useSections: (select) => {
+      const [, force] = useState(0)
+      useEffect(() => {
+        const listener = () => { force(n => n + 1) }
+        listeners.add(listener)
+        return () => { listeners.delete(listener) }
+      }, [])
+      return select(current)
     },
-    sections: () => current,
     renderSlot,
   }
   const view = render(<SettingsRoot {...props} />)
   const bump = (next: Row[]) => {
     act(() => {
       current = next
-      version += 1
       for (const fn of [...listeners]) fn()
     })
   }