Sync CloudShell backend PTY size on terminal resize (#2553)

* Sync CloudShell backend PTY size on terminal resize

Resizing the browser window only re-fit the local xterm; the remote shell kept its original column count, so typed input wrapped/broke at the wrong column. Add resizeTerminal() client call to the CloudShell terminals/{id}/size endpoint and register a debounced terminal.onResize handler that pushes new dimensions to the backend.

* Add unit tests for registerTerminalResizeHandler (debounce, no-op skip, error handling)

* Fix resizeTerminal success test: stub a successful fetch response

src/Explorer/Tabs/CloudShellTab/Data/CloudShellClient.test.tsx

@@ -6,6 +6,7 @@ import {
   provisionConsole,
   putEphemeralUserSettings,
   registerCloudShellProvider,
+  resizeTerminal,
   verifyCloudShellProviderRegistration,
 } from "./CloudShellClient";
 
@@ -340,4 +341,66 @@ describe("CloudShellClient", () => {
       );
     });
   });
+
+  describe("resizeTerminal", () => {
+    it("should call fetch with correct parameters", async () => {
+      const consoleUri = "https://shell.azure.com/console123";
+      const terminalId = "terminal-id";
+      const size = { rows: 40, cols: 120 };
+
+      global.fetch = jest.fn().mockImplementationOnce(() => {
+        return {
+          ok: true,
+          status: 200,
+          json: jest.fn().mockResolvedValue({}),
+          text: jest.fn().mockResolvedValue(""),
+          headers: new Headers(),
+        } as unknown as Promise<Response>;
+      });
+
+      await resizeTerminal(consoleUri, terminalId, size);
+
+      expect(global.fetch).toHaveBeenCalledWith(
+        "https://shell.azure.com/console123/terminals/terminal-id/size?cols=120&rows=40&version=2019-01-01",
+        {
+          method: "POST",
+          headers: {
+            Accept: "application/json",
+            "Content-Type": "application/json",
+            "Content-Length": "2",
+            Authorization: "Bearer mock-token",
+            "x-ms-client-request-id": "mocked-uuid",
+            "Accept-Language": "en-US",
+          },
+          body: "{}",
+        },
+      );
+    });
+
+    it("should handle errors when terminal resize fails", async () => {
+      const consoleUri = "https://shell.azure.com/console123";
+      const terminalId = "terminal-id";
+      const size = { rows: 40, cols: 120 };
+
+      global.fetch = jest.fn().mockImplementationOnce(() => {
+        return {
+          ok: false,
+          status: 500,
+          statusText: "Internal Server Error",
+          json: jest.fn().mockRejectedValue(new Error("Failed to parse JSON")),
+          text: jest.fn().mockResolvedValue("Server Error"),
+          headers: new Headers(),
+        } as unknown as Promise<Response>;
+      });
+
+      await expect(resizeTerminal(consoleUri, terminalId, size)).rejects.toThrow(
+        "Failed to resize terminal: 500 Internal Server Error",
+      );
+
+      expect(global.fetch).toHaveBeenCalledWith(
+        "https://shell.azure.com/console123/terminals/terminal-id/size?cols=120&rows=40&version=2019-01-01",
+        expect.any(Object),
+      );
+    });
+  });
 });