🖍️ fix: Honor Agent Image Detail Settings (#15407)

* 🖼️ fix: Apply an Agent's Configured Image Detail

The Agent Builder exposes an Image Detail slider and saves it to
`model_parameters.imageDetail`, but nothing ever read it back: `encodeAndFormat`
resolves the level from `req.body.imageDetail`, which the agents route never
populates, so every image was encoded as `detail: "auto"`. Providers that reject
`auto` — MiniMax's OpenAI-compatible API among them — fail every image upload
through an agent, and the setting that would fix it has no effect.

The root cause is a classification error rather than a missing argument.
`extractLibreChatParams` splits LibreChat's own settings out of an agent's model
parameters, and its key set is derived from the `librechat` group in
`parameterSettings`. `imageDetail` sat in `baseDefinitions` instead, so it was
neither extracted for LibreChat's use nor stripped from the options handed to the
provider.

It is now grouped with `resendFiles` and the other LibreChat-level parameters,
which gives it the same path those already take: extracted during agent
initialization, carried on the initialized agent, passed to the client, and read
by `encodeAndFormat`. `AgentClient.getSaveOptions` already expected
`options.imageDetail` — nothing had ever populated it.

The request body still wins where it is set, so the classic endpoints keep
resolving detail from conversation settings exactly as before.

Fixes #15359

* 🔤 fix: Type Image Detail as Its Enum, Not a Bare String

`TConversation.imageDetail` is the `ImageDetail` enum, so the extractor's return
type and the initialized agent's field are now declared as that enum rather than
widened to `string`, and the tests pass enum members instead of raw literals.

Caught by CI's type check, which I had run before adding the tests and not after —
jest compiles the specs through babel, so the suite stayed green over a type error.

api/server/controllers/agents/client.imageDetail.spec.js

@@ -0,0 +1,55 @@
+const mockEncodeAndFormat = jest.fn().mockResolvedValue({ files: [], image_urls: [] });
+
+jest.mock('~/server/services/Files/images/encode', () => ({
+  encodeAndFormat: (...args) => mockEncodeAndFormat(...args),
+}));
+
+const AgentClient = require('./client');
+
+describe('AgentClient.addImageURLs - image detail', () => {
+  const buildClient = (options) => {
+    const client = Object.create(AgentClient.prototype);
+    client.options = {
+      req: { body: {} },
+      endpoint: 'agents',
+      agent: { id: 'agent_1', provider: 'openai' },
+      ...options,
+    };
+    return client;
+  };
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it("forwards the agent's configured detail to the encoder", async () => {
+    const client = buildClient({ imageDetail: 'high' });
+
+    await client.addImageURLs({}, [{ file_id: 'f_1' }]);
+
+    expect(mockEncodeAndFormat).toHaveBeenCalledTimes(1);
+    expect(mockEncodeAndFormat.mock.calls[0][2]).toEqual(
+      expect.objectContaining({ imageDetail: 'high' }),
+    );
+  });
+
+  it('leaves the detail undefined when the agent configures none, so the encoder falls back', async () => {
+    const client = buildClient({});
+
+    await client.addImageURLs({}, [{ file_id: 'f_1' }]);
+
+    expect(mockEncodeAndFormat.mock.calls[0][2].imageDetail).toBeUndefined();
+  });
+
+  it('still passes the provider and endpoint alongside the detail', async () => {
+    const client = buildClient({ imageDetail: 'low' });
+
+    await client.addImageURLs({}, [{ file_id: 'f_1' }]);
+
+    expect(mockEncodeAndFormat.mock.calls[0][2]).toEqual({
+      provider: 'openai',
+      endpoint: 'agents',
+      imageDetail: 'low',
+    });
+  });
+});

api/server/controllers/agents/client.js

@@ -1675,6 +1675,7 @@ class AgentClient extends BaseClient {
       {
         provider: this.options.agent.provider,
         endpoint: this.options.endpoint,
+        imageDetail: this.options.imageDetail,
       },
       VisionModes.agents,
     );