fix: what the batch C review found

- A redirect followed for a custom base URL (quota on) no longer carries
  the user's key or cookies to another origin, as fetch itself does, and
  a private address may redirect to another private one (already counted).
- The admin Test of an Ollama or Vertex AI entry without a URL goes where
  chat sends that entry's key: the environment's own URL variable, for
  Ollama else the local default. The Test of an Ollama Cloud key without
  a URL went to the cloud while chat went to local Ollama.
- Chat saves: each save notes the chat on screen and the order of the
  reads before reading its data. A save read before switching chats no
  longer writes into the chat switched to, and a copy that waited for its
  thumbnail no longer replaces a newer one.
- "Continue without saving" keeps its button when a later auto-save fails,
  and goes away when a new message is sent.
- A screenshot check that was waiting for its image when the user pressed
  Stop stays skipped after the next message.
- MCP History: draw.io's own copy of a diagram (after get_diagram) no
  longer adds an entry without a picture; a change of background is still
  its own version. The tab ignores an edit's answer that arrives after a
  newer AI write loaded.
- Desktop: a deleted preset is not brought back by a failed switch, and a
  request naming no preset does not stop a rollback. An origin keeping
  an access code counts as having settings.
- .env: a quoted value ending in a backslash ("C:\dir\") is read as dotenv
  reads it.
- The tool card no longer crashes on an id that does not turn into text;
  an older Test's success timer no longer ends a newer Test's spinner.
- Tests that passed without their fix now check it.

tests/unit/admin-test-model.test.ts

@@ -11,13 +11,19 @@ vi.mock("@/app/api/validate-model/route", () => ({
     },
 }))
 vi.mock("@/lib/admin/auth", () => ({ checkAdminAuth: () => null }))
-vi.mock("@/lib/admin/settings", () => ({ loadSettings: () => ({}) }))
+// The environment's own values, under the panel's settings
+const envFallback = vi.hoisted(() => ({ values: {} as Record<string, string> }))
+vi.mock("@/lib/admin/settings", () => ({
+    loadSettings: () => ({}),
+    getEnvFallback: (key: string) => envFallback.values[key] ?? null,
+}))
 
 import { POST as testModel } from "@/app/api/admin/test-model/route"
 
 const ENV = ["OPENAI_BASE_URL", "SGLANG_BASE_URL", "AI_GATEWAY_BASE_URL"]
 const saved: Record<string, string | undefined> = {}
 beforeEach(() => {
+    envFallback.values = {}
     for (const k of ENV) {
         saved[k] = process.env[k]
         delete process.env[k]
@@ -74,8 +80,25 @@ describe("admin Test of an entry without a URL", () => {
         try {
             await test({ provider: "vertexai", vertexApiKey: "new-key" })
             expect(sent.body.baseUrl).toBeUndefined()
+            // The environment's own URL, which chat uses once it is saved
+            envFallback.values.GOOGLE_VERTEX_BASE_URL =
+                "https://vertex-proxy.example.com"
+            await test({ provider: "vertexai", vertexApiKey: "new-key" })
+            expect(sent.body.baseUrl).toBe("https://vertex-proxy.example.com")
+            expect(sent.body.serverBaseUrl).toBe(true)
         } finally {
             delete process.env.GOOGLE_VERTEX_BASE_URL
         }
     })
+
+    it("tests Ollama where chat sends the entry's key", async () => {
+        // Chat on the saved entry: OLLAMA_BASE_URL of the environment, else
+        // the SDK's local default (the Test used to go to Ollama Cloud)
+        await test({ provider: "ollama", apiKey: "k" })
+        expect(sent.body.baseUrl).toBe("http://127.0.0.1:11434/api")
+        expect(sent.body.serverBaseUrl).toBe(true)
+        envFallback.values.OLLAMA_BASE_URL = "http://gpu:11434/api"
+        await test({ provider: "ollama", apiKey: "k" })
+        expect(sent.body.baseUrl).toBe("http://gpu:11434/api")
+    })
 })