refactor(@angular/build): update MCP best practices guide content

The best practices guide that is provided by the Angular CLI's MCP server
has been updated with the latest available content.

(cherry picked from commit 48d7a03)

Author: clydin

packages/angular/cli/src/commands/mcp/instructions/best-practices.md

@@ -9,10 +9,12 @@ You are an expert in TypeScript, Angular, and scalable web application developme
 ## Angular Best Practices
 
 - Always use standalone components over NgModules
-- Don't use explicit `standalone: true` (it is implied by default)
+- Must NOT set `standalone: true` inside Angular decorators. It's the default.
 - Use signals for state management
 - Implement lazy loading for feature routes
+- Do NOT use the `@HostBinding` and `@HostListener` decorators. Put host bindings inside the `host` object of the `@Component` or `@Directive` decorator instead
 - Use `NgOptimizedImage` for all static images.
+  - `NgOptimizedImage` does not work for inline base64 images.
 
 ## Components
 
@@ -30,6 +32,7 @@ You are an expert in TypeScript, Angular, and scalable web application developme
 - Use signals for local component state
 - Use `computed()` for derived state
 - Keep state transformations pure and predictable
+- Do NOT use `mutate` on signals, use `update` or `set` instead
 
 ## Templates
 
@@ -42,3 +45,8 @@ You are an expert in TypeScript, Angular, and scalable web application developme
 - Design services around a single responsibility
 - Use the `providedIn: 'root'` option for singleton services
 - Use the `inject()` function instead of constructor injection
+
+## Common pitfalls
+
+- Control flow (`@if`):
+  - You cannot use `as` expressions in `@else if (...)`. E.g. invalid code: `@else if (bla(); as x)`.