feat(web): expose the agent-preset roster over the API

`agentPreset.list` gives a browser the deployment's roster so it can offer a
choice when starting a session. Each row carries the id, its `trust`, and
whether it is the current default.

`trust` is on the wire deliberately: a `user` preset is exactly as privileged
as the plugins it names, so a surface that offers one alongside a shipped
preset can say which is which rather than presenting both as vetted.

The domain is read-only. A preset is a composition on disk, so authoring one
is a filesystem act rather than an RPC; and a deployment composing no presets
answers with an empty roster rather than an error, because sharing the host
composition is a valid deployment.

The RPC map made every registration site a type error, so the route, the
response-schema table, the service delegate, and the browser fixture are all
wired rather than only the ones I remembered.

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

@@ -40,6 +40,7 @@ import {
 } from '../api/workspace.schema.ts'
 import { commandExecuteValueSchema, commandListValueSchema } from '../api/commands.schema.ts'
 import { skillListValueSchema } from '../api/skills.schema.ts'
+import { agentPresetListValueSchema } from '../api/agent-presets.schema.ts'
 import {
   goalCreateValueSchema,
   goalEditValueSchema,
@@ -119,6 +120,9 @@ export interface IApiClient {
   skills: {
     list(payload: RequestPayload<'skill.list'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'skill.list'>>>
   }
+  readonly agentPresets: {
+    list(payload: RequestPayload<'agentPreset.list'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'agentPreset.list'>>>
+  }
   events: {
     mux(payload: Parameters<ApiProxy['events']['mux']>[0]['payload'], signal: AbortSignal, onOpen?: () => void): AsyncIterable<RpcRequest<MuxFrame>>
     host(payload: Parameters<ApiProxy['events']['host']>[0]['payload'], signal: AbortSignal, onOpen?: () => void): AsyncIterable<RpcRequest<HostFrame>>
@@ -185,6 +189,7 @@ const UNARY_VALUE_SCHEMAS: { [K in keyof RpcMethodMap]: z.ZodType<Wire<ResponseV
   'command.list': commandListValueSchema,
   'command.execute': commandExecuteValueSchema,
   'skill.list': skillListValueSchema,
+  'agentPreset.list': agentPresetListValueSchema,
   'goal.create': goalCreateValueSchema,
   'goal.edit': goalEditValueSchema,
   'goal.pause': goalPauseValueSchema,
@@ -443,6 +448,11 @@ export abstract class AbstractApiClient implements IApiClient {
     list: (payload, signal) => this.callUnary('skill.list', payload, signal),
   }
 
+  readonly agentPresets = {
+    list: (payload: RequestPayload<'agentPreset.list'>, signal?: AbortSignal) =>
+      this.callUnary('agentPreset.list', payload, signal),
+  }
+
   readonly goals: IApiClient['goals'] = {
     create: (payload, signal) => this.callUnary('goal.create', payload, signal),
     edit: (payload, signal) => this.callUnary('goal.edit', payload, signal),

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

@@ -42,6 +42,7 @@ import {
 } from '../api/workspace.schema.ts'
 import { commandExecuteRequestSchema, commandListRequestSchema } from '../api/commands.schema.ts'
 import { skillListRequestSchema } from '../api/skills.schema.ts'
+import { agentPresetListRequestSchema } from '../api/agent-presets.schema.ts'
 import {
   goalCreateRequestSchema,
   goalEditRequestSchema,
@@ -109,6 +110,7 @@ const UNARY_ROUTES: UnaryRoutes = {
   'command.list': { schema: commandListRequestSchema, invoke: (api, r) => api.commands.list(r) },
   'command.execute': { schema: commandExecuteRequestSchema, invoke: (api, r, signal) => api.commands.execute(r, signal) },
   'skill.list': { schema: skillListRequestSchema, invoke: (api, r) => api.skills.list(r) },
+  'agentPreset.list': { schema: agentPresetListRequestSchema, invoke: (api, r) => api.agentPresets.list(r) },
   'goal.create': { schema: goalCreateRequestSchema, invoke: (api, r) => api.goals.create(r) },
   'goal.edit': { schema: goalEditRequestSchema, invoke: (api, r) => api.goals.edit(r) },
   'goal.pause': { schema: goalPauseRequestSchema, invoke: (api, r) => api.goals.pause(r) },