Fix provider baseUrl stripping endpoint suffixes before /models

Task: Fix provider baseUrl stripping endpoint suffixes before /models

## Problem
When users entered a full endpoint URL as the provider base URL (e.g.
`https://api.openai.com/v1/chat/completions` instead of
`https://api.openai.com/v1`), the server would append `/models` to it,
producing the invalid path `/v1/chat/completions/models` — resulting in
HTTP 404 errors for model discovery, connection tests, and analysis.

## Changes

### `artifacts/api-server/src/lib/aiAnalysis.ts`
- Added exported `normalizeBaseUrl(raw: string): string` helper that:
  - Strips trailing slashes
  - Strips known endpoint suffixes: `/chat/completions`, `/completions`, `/messages`
  - Strips trailing slashes again after suffix removal
- Applied `normalizeBaseUrl` in `callOpenAiCompatible`, `callAnthropic`,
  and `listProviderModels` (replacing the previous bare `.replace(/\/$/, "")`)

### `artifacts/api-server/src/routes/providers.ts`
- Imported `normalizeBaseUrl` from aiAnalysis
- Applied normalization to `baseUrl` in the POST /providers (create) handler
- Applied normalization to `baseUrl` in the PATCH /providers/:id (update) handler
- This ensures the canonical normalized value is persisted from the start

### `artifacts/api-server/src/routes/providers.listModels.test.ts`
- Added import of `normalizeBaseUrl`
- Added a new `describe("normalizeBaseUrl")` block with 7 unit tests covering:
  all three suffix patterns, trailing slashes, clean URLs, combined suffix+slash,
  and non-matching partial suffixes

## Test results
All 13 tests pass (6 existing + 7 new normalization unit tests).

Replit-Task-Id: 9ab5c336-d54e-4bc3-8f01-0b7486365c4b

artifacts/api-server/src/lib/aiAnalysis.ts

@@ -101,12 +101,25 @@ function extractJson(text: string): unknown {
   return JSON.parse(candidate.slice(start, end + 1));
 }
 
+const ENDPOINT_SUFFIXES = ["/chat/completions", "/completions", "/messages"];
+
+export function normalizeBaseUrl(raw: string): string {
+  let url = raw.replace(/\/+$/, "");
+  for (const suffix of ENDPOINT_SUFFIXES) {
+    if (url.endsWith(suffix)) {
+      url = url.slice(0, url.length - suffix.length).replace(/\/+$/, "");
+      break;
+    }
+  }
+  return url;
+}
+
 async function callOpenAiCompatible(
   provider: AiProvider,
   system: string,
   user: string,
 ): Promise<string> {
-  const base = provider.baseUrl.replace(/\/$/, "");
+  const base = normalizeBaseUrl(provider.baseUrl);
   const url = `${base}/chat/completions`;
   const res = await fetchWithTimeout(url, {
     method: "POST",
@@ -139,7 +152,7 @@ async function callAnthropic(
   system: string,
   user: string,
 ): Promise<string> {
-  const base = provider.baseUrl.replace(/\/$/, "");
+  const base = normalizeBaseUrl(provider.baseUrl);
   const url = `${base}/messages`;
   const res = await fetchWithTimeout(url, {
     method: "POST",
@@ -179,7 +192,7 @@ export async function callProvider(
 export async function listProviderModels(
   provider: AiProvider,
 ): Promise<string[]> {
-  const base = provider.baseUrl.replace(/\/$/, "");
+  const base = normalizeBaseUrl(provider.baseUrl);
   const url = `${base}/models`;
   const headers: Record<string, string> =
     provider.apiType === "anthropic"

artifacts/api-server/src/routes/providers.listModels.test.ts

@@ -7,6 +7,7 @@ import {
   afterEach,
   vi,
 } from "vitest";
+import { normalizeBaseUrl } from "../lib/aiAnalysis";
 import type { AddressInfo } from "node:net";
 import type { Server } from "node:http";
 
@@ -301,3 +302,47 @@ describe("POST /api/providers/list-models", () => {
     expect(json.message).not.toContain(token);
   });
 });
+
+describe("normalizeBaseUrl", () => {
+  it("strips /chat/completions suffix", () => {
+    expect(normalizeBaseUrl("https://api.openai.com/v1/chat/completions")).toBe(
+      "https://api.openai.com/v1",
+    );
+  });
+
+  it("strips /completions suffix", () => {
+    expect(normalizeBaseUrl("https://api.example.com/v1/completions")).toBe(
+      "https://api.example.com/v1",
+    );
+  });
+
+  it("strips /messages suffix", () => {
+    expect(normalizeBaseUrl("https://api.anthropic.com/v1/messages")).toBe(
+      "https://api.anthropic.com/v1",
+    );
+  });
+
+  it("strips trailing slashes without a known suffix", () => {
+    expect(normalizeBaseUrl("https://api.example.com/v1/")).toBe(
+      "https://api.example.com/v1",
+    );
+  });
+
+  it("leaves a clean base URL unchanged", () => {
+    expect(normalizeBaseUrl("https://api.example.com/v1")).toBe(
+      "https://api.example.com/v1",
+    );
+  });
+
+  it("strips trailing slash after known suffix is removed", () => {
+    expect(normalizeBaseUrl("https://api.example.com/v1/completions/")).toBe(
+      "https://api.example.com/v1",
+    );
+  });
+
+  it("does not strip partial suffix matches (e.g. /completions-extra)", () => {
+    expect(
+      normalizeBaseUrl("https://api.example.com/v1/completions-extra"),
+    ).toBe("https://api.example.com/v1/completions-extra");
+  });
+});

artifacts/api-server/src/routes/providers.ts

@@ -15,7 +15,7 @@ import {
   ListProviderModelsBody,
   ListProviderModelsResponse,
 } from "@workspace/api-zod";
-import { callProvider, listProviderModels } from "../lib/aiAnalysis";
+import { callProvider, listProviderModels, normalizeBaseUrl } from "../lib/aiAnalysis";
 import { t, reqLang } from "../lib/i18n";
 
 const router: IRouter = Router();
@@ -57,7 +57,7 @@ router.post("/providers", async (req, res) => {
     .values({
       name: d.name,
       apiType: d.apiType,
-      baseUrl: d.baseUrl,
+      baseUrl: normalizeBaseUrl(d.baseUrl),
       model: d.model,
       apiToken: d.apiToken ?? null,
       enabled: d.enabled ?? true,
@@ -81,7 +81,7 @@ router.patch("/providers/:id", async (req, res) => {
   const update: Partial<typeof aiProvidersTable.$inferInsert> = {};
   if (d.name !== undefined) update.name = d.name;
   if (d.apiType !== undefined) update.apiType = d.apiType;
-  if (d.baseUrl !== undefined) update.baseUrl = d.baseUrl;
+  if (d.baseUrl !== undefined) update.baseUrl = normalizeBaseUrl(d.baseUrl);
   if (d.model !== undefined) update.model = d.model;
   if (d.enabled !== undefined) update.enabled = d.enabled;
   if (d.apiToken !== undefined && d.apiToken !== "")