refactor: keep --app-name flag as non-deprecated for {{app}} placeholder

Remove deprecation from --app-name since it serves a valuable purpose for the {{app}} placeholder in custom strings, especially useful for internationalization. Update documentation to show how --app-name works with --custom-strings and clarify that only --welcome-text is deprecated.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: strickvl

docs/customization.md

@@ -95,40 +95,58 @@ docker run -it --name code-server -p 127.0.0.1:8080:8080 \
   }'
 ```
 
-## Legacy Support (Deprecated)
+## Using App Name with Custom Strings
 
-The following flags are still supported but deprecated. Use `--custom-strings` for new deployments:
+The `--app-name` flag works perfectly with `--custom-strings` to provide the `{{app}}` placeholder functionality:
 
 ```bash
-# Deprecated - use --custom-strings instead
 code-server \
-  --app-name "My Development Server" \
-  --welcome-text "Welcome to the development environment"
+  --app-name "Dev Portal" \
+  --custom-strings '{"WELCOME": "Welcome to {{app}} environment"}'
 ```
 
-These legacy flags will show deprecation warnings and may be removed in future versions.
+This approach allows you to:
+- Set a custom app name once with `--app-name`
+- Use `{{app}}` placeholders in your custom strings
+- Easily change the app name without updating all strings
 
-## Migration Guide
+### Examples with App Name
 
-### From Legacy Flags to Custom Strings
+**Corporate branding with dynamic app name:**
+```bash
+code-server \
+  --app-name "ACME Development Platform" \
+  --custom-strings '{
+    "WELCOME": "Welcome to {{app}}",
+    "LOGIN_TITLE": "{{app}} Access Portal",
+    "LOGIN_BELOW": "Please authenticate to access {{app}}"
+  }'
+```
 
-**Old approach:**
+**Internationalization with app name:**
 ```bash
 code-server \
-  --app-name "Dev Portal" \
-  --welcome-text "Welcome to development"
+  --app-name "Mon Portail" \
+  --custom-strings '{
+    "WELCOME": "Bienvenue sur {{app}}",
+    "LOGIN_TITLE": "Connexion à {{app}}",
+    "SUBMIT": "SE CONNECTER"
+  }'
 ```
 
-**New approach:**
+## Legacy Flag Migration
+
+The `--welcome-text` flag is deprecated. Migrate to `--custom-strings`:
+
+**Old:**
 ```bash
-code-server --custom-strings '{
-  "WELCOME": "Welcome to development"
-}'
+code-server --welcome-text "Welcome to development"
 ```
 
-**Note:** The `--app-name` flag controls the `{{app}}` placeholder in templates. You can either:
-1. Keep using `--app-name` alongside `--custom-strings`
-2. Customize the full text without placeholders in your JSON
+**New:**
+```bash
+code-server --custom-strings '{"WELCOME": "Welcome to development"}'
+```
 
 ## Benefits of Custom Strings
 

src/node/cli.ts

@@ -285,8 +285,7 @@ export const options: Options<Required<UserProvidedArgs>> = {
   "app-name": {
     type: "string",
     short: "an",
-    description: "The name to use in branding. Will be shown in titlebar and welcome message",
-    deprecated: true,
+    description: "Will replace the {{app}} placeholder in any strings, which by default includes the title bar and welcome message",
   },
   "welcome-text": {
     type: "string",

test/unit/node/cli.test.ts

@@ -366,7 +366,7 @@ describe("parser", () => {
     expect(() => parse(["--custom-strings", "/path/to/file.json"])).not.toThrow()
   })
 
-  it("should support deprecated app-name and welcome-text flags", async () => {
+  it("should support app-name and deprecated welcome-text flags", async () => {
     const args = parse(["--app-name", "My App", "--welcome-text", "Welcome!"])
     expect(args).toEqual({
       "app-name": "My App",