Feat/generic OpenAI provider (#68)

* feat: added a generic openai endpoint provider for self-hosted models

* feat: proper vision and tool checkbox for generic endpoint

---------

Co-authored-by: hugo <hugoms@me.com>

tests/engine/generic-openai-provider.test.ts

@@ -0,0 +1,58 @@
+/**
+ * Tests for generic OpenAI-compatible endpoint support in ProviderRegistry.
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { ProviderRegistry } from '../../src/main/engine/ai/providers';
+
+vi.mock('../../src/main/engine/ModelCatalogEngine', () => ({
+  ModelCatalogEngine: class {
+    getAll = vi.fn().mockResolvedValue([]);
+    getContextWindow = vi.fn().mockResolvedValue(null);
+  },
+}));
+
+describe('generic OpenAI-compatible provider support', () => {
+  let registry: ProviderRegistry;
+
+  beforeEach(() => {
+    registry = new ProviderRegistry();
+  });
+
+  it('fetchGenericOpenAIModels does not duplicate the v1 path when base URL already ends with /v1', async () => {
+    registry.setGenericOpenAIEnabled(true);
+    registry.setGenericOpenAIBaseURL('http://localhost:4000/v1');
+
+    const mockFetch = vi.fn().mockResolvedValue({
+      ok: true,
+      json: async () => ({
+        data: [{ id: 'custom-model' }],
+      }),
+    });
+    const originalFetch = globalThis.fetch;
+    globalThis.fetch = mockFetch;
+
+    try {
+      const models = await registry.fetchGenericOpenAIModels();
+      expect(mockFetch).toHaveBeenCalledWith(
+        'http://localhost:4000/v1/models',
+        expect.objectContaining({ method: 'GET', signal: expect.any(AbortSignal) }),
+      );
+      expect(models).toHaveLength(1);
+      expect(models[0]).toMatchObject({ id: 'custom-model', provider: 'generic-openai' });
+    } finally {
+      globalThis.fetch = originalFetch;
+    }
+  });
+
+  it('does not treat generic endpoint models as local when airplane mode is active', () => {
+    registry.setGenericOpenAIEnabled(true);
+    registry.setGenericOpenAIBaseURL('http://localhost:4000/v1');
+    registry.registerGenericOpenAIModel('custom-model');
+    registry.setOfflineMode(true);
+
+    expect(registry.isReady()).toBe(false);
+    expect(registry.getKnownLocalModels()).toEqual([]);
+    expect(() => registry.resolveModel('custom-model')).toThrow(/not available offline/i);
+  });
+});