Feature: Add local OpenAI-compatible model discovery to /model (#201)

* Add local OpenAI-compatible model discovery to /model

* Guard local OpenAI model discovery from Codex routing

* Preserve remote OpenAI Codex alias behavior

src/utils/providerDiscovery.test.ts

@@ -0,0 +1,78 @@
+import { afterEach, expect, mock, test } from 'bun:test'
+
+import {
+  getLocalOpenAICompatibleProviderLabel,
+  listOpenAICompatibleModels,
+} from './providerDiscovery.js'
+
+const originalFetch = globalThis.fetch
+const originalEnv = {
+  OPENAI_BASE_URL: process.env.OPENAI_BASE_URL,
+}
+
+afterEach(() => {
+  globalThis.fetch = originalFetch
+  process.env.OPENAI_BASE_URL = originalEnv.OPENAI_BASE_URL
+})
+
+test('lists models from a local openai-compatible /models endpoint', async () => {
+  globalThis.fetch = mock((input, init) => {
+    const url = typeof input === 'string' ? input : input.url
+    expect(url).toBe('http://localhost:1234/v1/models')
+    expect(init?.headers).toEqual({ Authorization: 'Bearer local-key' })
+
+    return Promise.resolve(
+      new Response(
+        JSON.stringify({
+          data: [
+            { id: 'qwen2.5-coder-7b-instruct' },
+            { id: 'llama-3.2-3b-instruct' },
+            { id: 'qwen2.5-coder-7b-instruct' },
+          ],
+        }),
+        { status: 200 },
+      ),
+    )
+  }) as typeof globalThis.fetch
+
+  await expect(
+    listOpenAICompatibleModels({
+      baseUrl: 'http://localhost:1234/v1',
+      apiKey: 'local-key',
+    }),
+  ).resolves.toEqual([
+    'qwen2.5-coder-7b-instruct',
+    'llama-3.2-3b-instruct',
+  ])
+})
+
+test('returns null when a local openai-compatible /models request fails', async () => {
+  globalThis.fetch = mock(() =>
+    Promise.resolve(new Response('not available', { status: 503 })),
+  ) as typeof globalThis.fetch
+
+  await expect(
+    listOpenAICompatibleModels({ baseUrl: 'http://localhost:1234/v1' }),
+  ).resolves.toBeNull()
+})
+
+test('detects LM Studio from the default localhost port', () => {
+  expect(getLocalOpenAICompatibleProviderLabel('http://localhost:1234/v1')).toBe(
+    'LM Studio',
+  )
+})
+
+test('detects common local openai-compatible providers by hostname', () => {
+  expect(
+    getLocalOpenAICompatibleProviderLabel('http://localai.local:8080/v1'),
+  ).toBe('LocalAI')
+  expect(
+    getLocalOpenAICompatibleProviderLabel('http://vllm.local:8000/v1'),
+  ).toBe('vLLM')
+})
+
+test('falls back to a generic local openai-compatible label', () => {
+  expect(
+    getLocalOpenAICompatibleProviderLabel('http://127.0.0.1:8080/v1'),
+  ).toBe('Local OpenAI-compatible')
+})