refactor(gui): slot system standard — single register, four props shares, framework store seat

The definitive slot model for the web client, replacing the first-generation
define/register two-step, ScopedSlots whitelist faces, and binding handles:

- 'root' is the only a-priori slot (SlotsService built-in); the shell renders
  exactly ctx.slots.renderSlot('root', {}).
- register is the single API: children = slot declaration + render
  authorization + runtime spec in one options object; misconfiguration fails
  loud at load (duplicate declaration, undeclared contribution, one store
  handle under two scopes).
- Component props arrive in four auto-derived shares: PropsRuntime<K>
  (owner params + session/global standard kits via declare-merge),
  PropsRenderSlots<S>, PropsStore<H>, and the inject business face.
  sessionId is framework-supplied; hooks are framework-made only.
- Framework store seat: defineStore factories declare schema/actions/persist;
  read = useStore, write = baked actions only; store scope derives from the
  mounting entry; per-session persist keys and clearPersisted lifecycle.
- inject factories read the apply closure's own ctx (binding handles retired;
  root-ctx back door closed); SessionProvider is self-wired render-prop.
- Rendering sits behind the SlotRenderer install seam; runtime stays
  React-free; ownership ledger keyed to the single entry axis closes the
  stale-authority window (StaleAuthorizationError probes).

Docs: the slot type-chain note is refreshed in place as the slot system
standard RFC (bilingual pair re-recorded); the web client architecture RFC
defers its slot sections there; packages/client/AGENTS.md gains the slot and
props discipline; gui-testing/web-styling notes drop missions/ references.

Tests: suites rewritten to the standard (props fed directly, real store
engines via createXXXStore().create(), no render machinery); load-time
negative samples for declaration/authorization/store conflicts; verified by
real-host playwright run (three columns, empty state, collapse, keyed session
remount, cross-slot selection sharing).

docs(ui-sidebar): point contract reference at the committed slot standard RFC

missions/ is workspace-local and never committed; the README must not cite it.

packages/client/ui-layout/tests/apply.spec.ts

@@ -1,15 +1,14 @@
 // @vitest-environment jsdom
-// Client apply wiring: ctx.layout provided, the four layout-owned slots
-// defined, teardown cascades (service unprovided + slot specs removed + list
-// subscription dropped). Node half and the invariant companion ride along —
-// they are one-line surfaces the aggregate coverage gate still requires
-// exercised.
+// Client apply wiring under the terminal register form: ctx.layout provided,
+// ONE register() call declares the four child slots + seats the store factory
+// + wires the panel actions through the inject hook; teardown cascades
+// (service unprovided + declarations gone + registration cleared). Node half
+// and the invariant companion ride along — one-line surfaces the aggregate
+// coverage gate still requires exercised.
 
 import { Context } from 'cordis'
 import { describe, expect, it, vi } from 'vitest'
-import { createSnapshotStore } from '@deepseek-ai/dsh-client-web-react'
 import { SlotsService } from '@deepseek-ai/dsh-client-runtime/client'
-import type { SessionListState } from '@deepseek-ai/dsh-client-runtime/client'
 import { apply, inject, LayoutService } from '@deepseek-ai/dsh-client-ui-layout/client'
 import { apply as nodeApply } from '@deepseek-ai/dsh-client-ui-layout'
 import * as invariant from '@deepseek-ai/dsh-client-ui-layout/invariant'
@@ -18,8 +17,6 @@ async function bench() {
   const ctx = new Context()
   const slotsFiber = ctx.plugin(SlotsService)
   await slotsFiber.await()
-  const list = createSnapshotStore<SessionListState>({ ids: [], byId: {} })
-  ctx.provide('sessions', { list })
   return { ctx, slots: ctx.get('slots') as SlotsService }
 }
 
@@ -28,28 +25,31 @@ describe('ui-layout client apply', () => {
     expect(inject).toContain('slots')
   })
 
-  it('provides ctx.layout and defines the four layout-owned slots', async () => {
+  it('provides ctx.layout and registers AppFrame into root with the four child declarations', async () => {
     const { ctx, slots } = await bench()
     const fiber = ctx.plugin({ inject: ['slots'], apply })
     await fiber.await()
     expect(ctx.get('layout')).toBeInstanceOf(LayoutService)
+    // The one register() call occupied 'root'…
+    expect(slots.entries('root')).toHaveLength(1)
+    // …and declared the four children in the ledger.
     expect(slots.spec('sidebar')).toEqual({ kind: 'single', scope: 'root' })
     expect(slots.spec('conversation')).toEqual({ kind: 'single', scope: 'session' })
     expect(slots.spec('details')).toEqual({ kind: 'single', scope: 'session' })
     expect(slots.spec('conversation.empty')).toEqual({ kind: 'single', scope: 'root' })
   })
 
-  it('teardown unwinds service, slot specs, and the prune subscription', async () => {
+  it('teardown unwinds the service, the root registration, and the child declarations', async () => {
     const { ctx, slots } = await bench()
     const fiber = ctx.plugin({ inject: ['slots'], apply })
     await fiber.await()
-    const layout = ctx.get('layout') as LayoutService
-    const disposeSpy = vi.spyOn(layout, 'dispose')
     await fiber.dispose()
     expect(ctx.get('layout')).toBeUndefined()
+    expect(slots.entries('root')).toHaveLength(0)
     expect(slots.spec('sidebar')).toBeUndefined()
     expect(slots.spec('conversation.empty')).toBeUndefined()
-    expect(disposeSpy).toHaveBeenCalledTimes(1)
+    // The built-in root declaration survives entry teardown (runtime-owned).
+    expect(slots.spec('root')).toEqual({ kind: 'single', scope: 'root' })
   })
 })