feat(settings): link to each provider's key page and clean up base URLs

- A "Get API key" link next to the API Key field for the 19 providers
  that have a key page (from env.example and the providers' docs). 17
  answered 200 to curl; OpenAI's is behind a Cloudflare challenge and
  DeepSeek's behind a regional block, both checked in Chrome
- Base URLs drop spaces, trailing slashes and a pasted endpoint path
  (/chat/completions, /completions, /messages, /responses), which the
  SDK would otherwise append a second time and get a 404. getAIModel does
  this for the chat and the Test button; the field does it on blur and
  shows the URL requests go to

tests/e2e/model-test.spec.ts

@@ -65,3 +65,34 @@ test("the Test button checks all models at once and shows each result", async ({
         "model-ok",
     ])
 })
+
+test("the key link and the base URL cleanup", async ({ page }) => {
+    await page.addInitScript((config) => {
+        localStorage.setItem(
+            "next-ai-draw-io-model-configs",
+            JSON.stringify(config),
+        )
+    }, CONFIG)
+    await page.goto("/", { waitUntil: "networkidle" })
+    await getIframe(page).waitFor({ state: "visible", timeout: 30000 })
+    await page.locator("button:has(svg.lucide-bot)").first().click()
+    await page.getByText("Configure Models...").click()
+    const dialog = page.locator('[role="dialog"]')
+    await dialog.getByText("GLM (Zhipu)").first().click()
+
+    await expect(
+        dialog.getByRole("link", { name: "Get API key" }),
+    ).toHaveAttribute(
+        "href",
+        "https://open.bigmodel.cn/usercenter/proj-mgmt/apikeys",
+    )
+    const baseUrl = dialog.locator("#base-url")
+    await baseUrl.fill("https://proxy.example.com/v4/chat/completions/")
+    await baseUrl.blur()
+    await expect(baseUrl).toHaveValue("https://proxy.example.com/v4")
+    await expect(
+        dialog.getByText(
+            "Requests go to https://proxy.example.com/v4/chat/completions",
+        ),
+    ).toBeVisible()
+})

tests/unit/ai-providers.test.ts

@@ -332,6 +332,21 @@ describe("Atlas Cloud provider", () => {
             includeUsage: true,
         })
     })
+
+    it("drops an endpoint path pasted along with the base URL", () => {
+        getAIModel({
+            provider: "atlascloud",
+            apiKey: "client-atlas-key",
+            baseUrl: "https://proxy.example.com/v1/chat/completions/",
+            modelId: "deepseek-ai/deepseek-v4-pro",
+        })
+
+        expect(createCompatibleMock).toHaveBeenCalledWith(
+            expect.objectContaining({
+                baseURL: "https://proxy.example.com/v1",
+            }),
+        )
+    })
 })
 
 describe("Kimi provider uses createDeepSeek for reasoning_content support", () => {

tests/unit/base-url.test.ts

@@ -0,0 +1,42 @@
+import { describe, expect, it } from "vitest"
+import { chatRequestUrl, normalizeBaseUrl } from "@/lib/types/model-config"
+
+describe("normalizeBaseUrl", () => {
+    it("drops spaces, trailing slashes and a pasted endpoint path", () => {
+        expect(normalizeBaseUrl(" https://api.x.com/v1/ ")).toBe(
+            "https://api.x.com/v1",
+        )
+        expect(normalizeBaseUrl("https://api.x.com/v1/chat/completions")).toBe(
+            "https://api.x.com/v1",
+        )
+        expect(
+            normalizeBaseUrl("https://api.x.com/anthropic/v1/messages/"),
+        ).toBe("https://api.x.com/anthropic/v1")
+    })
+
+    it("keeps provider paths such as /api/paas/v4 and /api/v3", () => {
+        expect(normalizeBaseUrl("https://open.bigmodel.cn/api/paas/v4")).toBe(
+            "https://open.bigmodel.cn/api/paas/v4",
+        )
+        expect(
+            normalizeBaseUrl("https://ark.cn-beijing.volces.com/api/v3"),
+        ).toBe("https://ark.cn-beijing.volces.com/api/v3")
+    })
+})
+
+describe("chatRequestUrl", () => {
+    it("shows the endpoint the SDK will call", () => {
+        expect(chatRequestUrl("glm", "https://api.x.com/v1/")).toBe(
+            "https://api.x.com/v1/chat/completions",
+        )
+        expect(
+            chatRequestUrl("anthropic", "https://proxy.example.com/v1"),
+        ).toBe("https://proxy.example.com/v1/messages")
+    })
+
+    it("stays out of the way for SDKs that build their own paths", () => {
+        expect(chatRequestUrl("google", "https://x.example.com")).toBeNull()
+        expect(chatRequestUrl("minimax", "https://x.example.com")).toBeNull()
+        expect(chatRequestUrl("glm", "  ")).toBeNull()
+    })
+})