feat: support session-scoped model overrides

Model selection was acting like a provider-level preference.

That made resumed sessions drift back to a default or request-time model.

Users expect /models changes made inside a conversation to affect that session.

Store explicit session choices in app-owned ~/.cloudcli state.

This avoids editing provider transcripts or native provider config.

Resolve the effective model before launching each provider runtime.

Claude, Cursor, Codex, Gemini, and OpenCode now honor stored resume choices.

Expose a backend active-model change endpoint for existing sessions.

The models modal can now distinguish default changes from session overrides.

It also shows when a selected model will apply on the next response.

For Claude, stop probing active model state by resuming with a dummy prompt.

Read the indexed JSONL transcript from the end instead.

This preserves provider history while honoring /model stdout or model fields.

Add service tests for adapter delegation and resume-model precedence.

The tests keep cache state, override state, and requested fallback separate.

server/modules/providers/services/provider-models.service.ts

@@ -6,11 +6,14 @@ import { providerRegistry } from '@/modules/providers/provider.registry.js';
 import type { IProvider } from '@/shared/interfaces.js';
 import type {
   LLMProvider,
+  ProviderChangeActiveModelInput,
   ProviderCurrentActiveModel,
   ProviderModelsCacheInfo,
   ProviderModelsDefinition,
   ProviderModelsResult,
+  ProviderSessionActiveModelChange,
 } from '@/shared/types.js';
+import { readProviderSessionActiveModelChange } from '@/shared/utils.js';
 
 export const PROVIDER_MODELS_CACHE_TTL_MS = 3 * 24 * 60 * 60 * 1000;
 const PROVIDER_MODELS_CACHE_VERSION = 1;
@@ -18,6 +21,7 @@ const PROVIDER_MODELS_CACHE_VERSION = 1;
 type ProviderModelsServiceDependencies = {
   resolveProvider?: (provider: LLMProvider) => Pick<IProvider, 'models'>;
   cachePath?: string;
+  activeModelChangesPath?: string;
   now?: () => number;
 };
 
@@ -132,6 +136,7 @@ const writeProviderModelsCacheFile = async (
 export const createProviderModelsService = (dependencies: ProviderModelsServiceDependencies = {}) => {
   const resolveProvider = dependencies.resolveProvider ?? providerRegistry.resolveProvider;
   const cachePath = dependencies.cachePath ?? getProviderModelsCachePath();
+  const activeModelChangesPath = dependencies.activeModelChangesPath;
   const now = dependencies.now ?? (() => Date.now());
   const memoryCache = new Map<LLMProvider, ProviderModelsCacheEntry>();
   const pendingRequests = new Map<LLMProvider, Promise<ProviderModelsResult>>();
@@ -270,6 +275,36 @@ export const createProviderModelsService = (dependencies: ProviderModelsServiceD
     sessionId?: string,
   ): Promise<ProviderCurrentActiveModel> => resolveProvider(provider).models.getCurrentActiveModel(sessionId);
 
+  const changeActiveModel = async (
+    provider: LLMProvider,
+    input: ProviderChangeActiveModelInput,
+  ): Promise<ProviderSessionActiveModelChange> => resolveProvider(provider).models.changeActiveModel(input);
+
+  const getChangedActiveModel = async (
+    provider: LLMProvider,
+    sessionId: string,
+  ): Promise<ProviderSessionActiveModelChange> => readProviderSessionActiveModelChange(provider, sessionId, {
+    filePath: activeModelChangesPath,
+  });
+
+  const resolveResumeModel = async (
+    provider: LLMProvider,
+    sessionId: string | undefined,
+    requestedModel?: string | null,
+  ): Promise<string | undefined> => {
+    const normalizedRequestedModel = typeof requestedModel === 'string' ? requestedModel.trim() : '';
+    if (!sessionId?.trim()) {
+      return normalizedRequestedModel || undefined;
+    }
+
+    const changedModel = await getChangedActiveModel(provider, sessionId);
+    if (changedModel.supported && changedModel.changed && changedModel.model?.trim()) {
+      return changedModel.model.trim();
+    }
+
+    return normalizedRequestedModel || undefined;
+  };
+
   const clearCache = (): void => {
     memoryCache.clear();
     pendingRequests.clear();
@@ -280,6 +315,9 @@ export const createProviderModelsService = (dependencies: ProviderModelsServiceD
   return {
     getProviderModels,
     getCurrentActiveModel,
+    getChangedActiveModel,
+    changeActiveModel,
+    resolveResumeModel,
     clearCache,
   };
 };