test: clarify Display Name field as optional in BYOK model dialog and update test plan to reflect behavior

Co-authored-by: Copilot <copilot@github.com>

Author: ethanyhou

com.microsoft.copilot.eclipse.swtbot.test/test-plans/byok/byok.md

@@ -289,9 +289,13 @@ Not exercised in this plan (separate scenarios):
 1. Open the BYOK page, select the **OpenAI** provider node, and click
    **Add Model…**.
 2. Verify the **Add OpenAI Models** dialog opens with fields **Model
-   ID** (required), **Display Name** (required), **Support Vision**
+   ID** (required), **Display Name** (optional), **Support Vision**
    checkbox, and **Support Tool Calling** checkbox. There is no
    deployment-URL or API-key field for OpenAI (those are Azure-only).
+   The **Add** button stays disabled until **Model ID** is non-blank;
+   leaving **Display Name** empty does **not** block the **Add** button
+   (validation only requires Model ID for non-Azure providers, and
+   additionally Deployment URL + API Key for Azure).
 3. Enter a model id (e.g. `gpt-4o-mini-test`), a display name (e.g.
    `My Custom Model`), leave the capability checkboxes at their defaults,
    and click **Add**.
@@ -304,15 +308,25 @@ Not exercised in this plan (separate scenarios):
    for it (custom models can be removed).
 7. Select any non-custom model in the same provider and verify **Remove
    Model** is **disabled** (default models cannot be removed).
+8. Re-open **Add Model…**, enter only a model id (e.g.
+   `gpt-4o-mini-blank-name`), leave **Display Name** empty, and click
+   **Add**. Verify the model is created and rendered in the tree using
+   the **model id** as its display name (the dialog falls back to the
+   trimmed model id when display name is blank — see
+   `AddByokModelDialog#buildModel`).
 
 #### Expected Result
 - The custom model is persisted, appears in the tree, and is selectable
   from the chat model picker after this point.
 - The OpenAI node count suffix updates to reflect the new model count.
+- When **Display Name** is left blank, the saved model's displayed name
+  equals the trimmed **Model ID**.
 
 #### 📸 Key Screenshots
 - [ ] **Add OpenAI Models dialog** with required fields filled.
 - [ ] **Custom model in tree** showing the new display name.
+- [ ] **Custom model in tree (blank display name)** — node label equals
+  the model id.
 
 ---
 

com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/preferences/AddByokModelDialog.java

@@ -89,7 +89,7 @@ protected Control createDialogArea(Composite parent) {
       createAzureSpecificFields(container);
     }
 
-    // Display Name (optional for all providers)
+    // Display Name
     new Label(container, SWT.NONE).setText(Messages.preferences_page_byok_addModel_displayName);
     displayNameText = new Text(container, SWT.BORDER);
     displayNameText.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false));