Merge origin/master: session projection base, command channel, composer seats

Resolution follows the reattachment plan: the #587 wire layer (planMode/
setPlanMode RPC, prompt.planMode, client Session projection fences) is
dropped in favor of the session-projection base now on master; master
structure wins in all shared files. Kept from the PR side: the approval-only
pending filter in ChatView (questions render solely through the composer
takeover) and the auto-merged QuestionComposer improvements. The deleted
host/runtime package and retired test carriers are removed with master.

packages/host/apiproxy/tests/client-handler.spec.ts

@@ -20,6 +20,8 @@ function ok<T>(request: RpcRequest<unknown>, value: T): Promise<RpcResponse<T>>
 function scriptedApi(overrides: {
   sessions?: Partial<ApiProxy['sessions']>
   host?: Partial<ApiProxy['host']>
+  commands?: Partial<ApiProxy['commands']>
+  skills?: Partial<ApiProxy['skills']>
   events?: Partial<ApiProxy['events']>
   respond?: ApiProxy['respond']
 } = {}): ApiProxy {
@@ -28,14 +30,44 @@ function scriptedApi(overrides: {
     sessions: {
       list: r => ok(r, { items: [] }),
       create: r => ok(r, { sessionId: sid('s-new') }),
-      history: r => ok(r, { events: [], hasMore: false }),
+      history: r => ok(r, {
+        events: [],
+        hasMore: false,
+        modelTarget: { provider: 'deepseek', model: 'deepseek-v4-flash' },
+      }),
+      models: r => ok(r, {
+        current: { provider: 'deepseek', model: 'deepseek-v4-flash' },
+        groups: [],
+        failures: [],
+      }),
+      selectModel: r => ok(r, {
+        selected: { provider: r.payload.provider, model: r.payload.model },
+      }),
       prompt: r => ok(r, { accepted: true as const }),
       cancel: r => ok(r, { accepted: true as const }),
       planMode: r => ok(r, null),
       setPlanMode: r => ok(r, null),
       ...overrides.sessions,
     },
-    host: { describe: r => ok(r, { version: '0-test', cwd: '/t', attachedSessions: 0 }), ...overrides.host },
+    host: {
+      describe: r => ok(r, { version: '0-test', cwd: '/t', attachedSessions: 0 }),
+      pickDirectory: r => ok(r, { path: null }),
+      openPath: r => ok(r, { opened: true as const }),
+      ...overrides.host,
+    },
+    workspace: {
+      list: r => ok(r, { items: [] }),
+      create: r => ok(r, { workspace: { workspaceId: 'w1' as never, path: '/t', title: 't', sessionIds: [], createdAt: '0', updatedAt: '0' }, created: true }),
+      rename: r => ok(r, { workspace: { workspaceId: 'w1' as never, path: '/t', title: 't', sessionIds: [], createdAt: '0', updatedAt: '0' } }),
+      delete: r => ok(r, { deleted: true as const }),
+      insertSessionBefore: r => ok(r, { workspace: { workspaceId: 'w1' as never, path: '/t', title: 't', sessionIds: [], createdAt: '0', updatedAt: '0' } }),
+    },
+    commands: {
+      list: r => ok(r, { commands: [] }),
+      execute: r => ok(r, { matched: false }),
+      ...overrides.commands,
+    },
+    skills: { list: r => ok(r, { skills: [] }), ...overrides.skills },
     events: { mux: () => empty<MuxFrame>(), host: () => empty<HostFrame>(), ...overrides.events },
     respond: overrides.respond ?? (() => Promise.resolve({ accepted: false as const, reason: 'not-pending' as const })),
   }
@@ -52,7 +84,7 @@ describe('unary round trip', () => {
       sessions: {
         list: (r) => {
           seen = r
-          return ok(r, { items: [{ sessionId: sid('s1'), updatedAt: 7, running: false }] })
+          return ok(r, { items: [{ sessionId: sid('s1'), updatedAt: 7, running: false, blank: false }] })
         },
       },
     })
@@ -61,7 +93,22 @@ describe('unary round trip', () => {
     expect(seen?.payload).toEqual({ cursor: 'c1' })
     expect(seen?.rpcId).toBeTruthy()
     expect(response.rpcId).toBe(seen?.rpcId)
-    expect(response.result).toEqual({ ok: true, value: { items: [{ sessionId: 's1', updatedAt: 7, running: false }] } })
+    expect(response.result).toEqual({ ok: true, value: { items: [{ sessionId: 's1', updatedAt: 7, running: false, blank: false }] } })
+  })
+
+  it('routes workspace rename, delete, and insertSessionBefore through the wire', async () => {
+    const api = scriptedApi()
+    const c = client(api)
+    const renamed = await c.workspace.rename({ workspaceId: 'w1' as never, title: 'next' })
+    expect(renamed.result.ok).toBe(true)
+    const blankTitle = await c.workspace.rename({ workspaceId: 'w1' as never, title: '   ' })
+    expect(blankTitle.result).toMatchObject({ ok: false, error: { code: 'bad-request' } })
+    const deleted = await c.workspace.delete({ workspaceId: 'w1' as never })
+    expect(deleted.result).toEqual({ ok: true, value: { deleted: true } })
+    const anchored = await c.workspace.insertSessionBefore({ workspaceId: 'w1' as never, sessionId: sid('s1'), beforeSessionId: sid('s2') })
+    expect(anchored.result.ok).toBe(true)
+    const appended = await c.workspace.insertSessionBefore({ workspaceId: 'w1' as never, sessionId: sid('s1') })
+    expect(appended.result.ok).toBe(true)
   })
 
   it('passes business errors through as 200 + err result, not a throw', async () => {
@@ -192,6 +239,23 @@ describe('unary round trip', () => {
   })
 })
 
+describe('workspace domain round trip', () => {
+  it('routes both workspace methods through their handler rows and value schemas', async () => {
+    const c = client(scriptedApi())
+    const list = await c.workspace.list({})
+    expect(list.result).toEqual({ ok: true, value: { items: [] } })
+    const created = await c.workspace.create({ path: '/t' })
+    expect(created.result.ok).toBe(true)
+    if (created.result.ok) expect(created.result.value.created).toBe(true)
+  })
+
+  it('rejects a create payload violating the exactly-one refine at the handler', async () => {
+    const response = await client(scriptedApi()).workspace.create({})
+    expect(response.result.ok).toBe(false)
+    if (!response.result.ok) expect(response.result.error.code).toBe('bad-request')
+  })
+})
+
 describe('SSE stream path', () => {
   it('yields frames in order and skips the comment preamble', async () => {
     const frames: MuxFrame[] = [
@@ -243,7 +307,7 @@ describe('SSE stream path', () => {
     const api = scriptedApi({
       events: {
         async *host(request): AsyncGenerator<RpcRequest<HostFrame>> {
-          yield { rpcId: RpcId(`p-${request.rpcId}`), payload: { type: 'host/session-added', sessionId: sid('s1') } }
+          yield { rpcId: RpcId(`p-${request.rpcId}`), payload: { type: 'host/session-added', sessionId: sid('s1'), blank: true } }
           throw new Error('impl died mid-stream')
         },
       },