feat(apiproxy): settings/credentials/llm wire domains, frames, and write guard

Eight compiler-locked methods: settings.describe/update/replace serve
redacted layered namespace views (secrets structurally absent from every
layer, write-only in the update direction) and fold seam refusals into
settings-rejected; credentials.describe/set/unset expose value-free views
with credential-rejected on shadowed writes; llm.providers merges the
configurable directory with live routes and llm.models claims the
host-scoped catalog reservation through the buildModelCatalog extraction
session.models now shares. Three HostFrame invalidations bridge the seam
events (host/settings-changed, host/credentials-changed,
host/models-changed), and the connection route generalizes the native-
dialog check into a privileged-method set covering all four writes. The
fixture and both fake clients grow the same face.

packages/host/apiproxy/src/api/rpc-map.ts

@@ -10,6 +10,9 @@ import type { WorkspaceApi } from './workspace.ts'
 import type { CommandsApi } from './commands.ts'
 import type { SkillsApi } from './skills.ts'
 import type { GoalsApi } from './goals.ts'
+import type { SettingsApi } from './settings.ts'
+import type { CredentialsApi } from './credentials.ts'
+import type { LlmApi } from './llm.ts'
 import type { RpcResponse } from './rpc.ts'
 
 /**
@@ -42,6 +45,14 @@ export interface RpcMethodMap {
   'goal.resume': GoalsApi['resume']
   'goal.complete': GoalsApi['complete']
   'goal.clear': GoalsApi['clear']
+  'settings.describe': SettingsApi['describe']
+  'settings.update': SettingsApi['update']
+  'settings.replace': SettingsApi['replace']
+  'credentials.describe': CredentialsApi['describe']
+  'credentials.set': CredentialsApi['set']
+  'credentials.unset': CredentialsApi['unset']
+  'llm.providers': LlmApi['providers']
+  'llm.models': LlmApi['models']
 }
 
 /** Business request payload of method K (reaches through the RpcRequest narrow form to payload). */