refactor(web): drop the permission RPC pair and turn-anchoring machinery

The session.permissions/setPermission unary pair, the PermissionOption wire
DTO, the client Session wrappers, and the fixture/fake mirrors all leave the
wire: the read side moves to the 'permissions' session projection and the
write side moves to the /permission command in follow-up commits, so the
web protocol gains no permission methods at all.

The pendingSwitches + prompt-submit flush + hasOpenTurn move also goes.
Knob events no longer need turn enclosure: the persistence scanner keeps
standalone events after the last turn/end as part of the preserved prefix
(remove-synthetic-log-only-turns), none of the three knob invariants demand
an open turn, and the setters append bare events. An idle switch commits
immediately; hasOpenTurn stays a user-approval private fold (its audit pair
is the one contract that still requires enclosure).

The old PermissionSelect chip and its mount-time fetch die with the RPCs
(the resident composer broke the mount-once assumption); the projection-fed
replacement lands with the Access seat swap.

packages/host/apiproxy/src/fetch/client.ts

@@ -22,10 +22,8 @@ import {
   sessionHistoryValueSchema,
   sessionListValueSchema,
   sessionModelsValueSchema,
-  sessionPermissionsValueSchema,
   sessionPromptValueSchema,
   sessionSelectModelValueSchema,
-  sessionSetPermissionValueSchema,
 } from '../api/sessions.schema.ts'
 import {
   workspaceCreateValueSchema,
@@ -61,8 +59,6 @@ export interface IApiClient {
     selectModel(payload: RequestPayload<'session.selectModel'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.selectModel'>>>
     prompt(payload: RequestPayload<'session.prompt'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.prompt'>>>
     cancel(payload: RequestPayload<'session.cancel'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.cancel'>>>
-    permissions(payload: RequestPayload<'session.permissions'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.permissions'>>>
-    setPermission(payload: RequestPayload<'session.setPermission'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.setPermission'>>>
   }
   host: {
     describe(payload: RequestPayload<'host.describe'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'host.describe'>>>
@@ -103,8 +99,6 @@ const UNARY_VALUE_SCHEMAS: { [K in keyof RpcMethodMap]: z.ZodType<Wire<ResponseV
   'session.selectModel': sessionSelectModelValueSchema,
   'session.prompt': sessionPromptValueSchema,
   'session.cancel': sessionCancelValueSchema,
-  'session.permissions': sessionPermissionsValueSchema,
-  'session.setPermission': sessionSetPermissionValueSchema,
   'host.describe': hostDescribeValueSchema,
   'host.pickDirectory': hostPickDirectoryValueSchema,
   'host.openPath': hostOpenPathValueSchema,
@@ -308,8 +302,6 @@ export abstract class AbstractApiClient implements IApiClient {
     selectModel: (payload, signal) => this.callUnary('session.selectModel', payload, signal),
     prompt: (payload, signal) => this.callUnary('session.prompt', payload, signal),
     cancel: (payload, signal) => this.callUnary('session.cancel', payload, signal),
-    permissions: (payload, signal) => this.callUnary('session.permissions', payload, signal),
-    setPermission: (payload, signal) => this.callUnary('session.setPermission', payload, signal),
   }
 
   readonly host: IApiClient['host'] = {

packages/host/apiproxy/src/fetch/handler.ts

@@ -20,10 +20,8 @@ import {
   sessionHistoryRequestSchema,
   sessionListRequestSchema,
   sessionModelsRequestSchema,
-  sessionPermissionsRequestSchema,
   sessionPromptRequestSchema,
   sessionSelectModelRequestSchema,
-  sessionSetPermissionRequestSchema,
 } from '../api/sessions.schema.ts'
 import {
   hostDescribeRequestSchema, hostOpenPathRequestSchema, hostPickDirectoryRequestSchema,
@@ -62,8 +60,6 @@ const UNARY_ROUTES: UnaryRoutes = {
   'session.selectModel': { schema: sessionSelectModelRequestSchema, invoke: (api, r) => api.sessions.selectModel(r) },
   'session.prompt': { schema: sessionPromptRequestSchema, invoke: (api, r) => api.sessions.prompt(r) },
   'session.cancel': { schema: sessionCancelRequestSchema, invoke: (api, r) => api.sessions.cancel(r) },
-  'session.permissions': { schema: sessionPermissionsRequestSchema, invoke: (api, r) => api.sessions.permissions(r) },
-  'session.setPermission': { schema: sessionSetPermissionRequestSchema, invoke: (api, r) => api.sessions.setPermission(r) },
   'host.describe': { schema: hostDescribeRequestSchema, invoke: (api, r) => api.host.describe(r) },
   'host.pickDirectory': { schema: hostPickDirectoryRequestSchema, invoke: (api, r, signal) => api.host.pickDirectory(r, signal) },
   'host.openPath': { schema: hostOpenPathRequestSchema, invoke: (api, r, signal) => api.host.openPath(r, signal) },