feat: salvage Angular developer skill

skills/angular-developer/references/resource.md

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+# Async Reactivity with `resource`
+
+> [!IMPORTANT]
+> The `resource` API is currently experimental in Angular.
+
+A `Resource` incorporates asynchronous data fetching into Angular's signal-based reactivity. It executes an async loader function whenever its dependencies change, exposing the status and result as synchronous signals.
+
+## Basic Usage
+
+The `resource` function accepts an options object with two main properties:
+
+1. `params`: A reactive computation (like `computed`). When signals read here change, the resource re-fetches.
+2. `loader`: An async function that fetches data based on the parameters.
+
+```ts
+import { Component, resource, signal, computed } from '@angular/core';
+
+@Component({...})
+export class UserProfile {
+  userId = signal('123');
+
+  userResource = resource({
+    // Reactively tracking userId
+    params: () => ({ id: this.userId() }),
+
+    // Executes whenever params change
+    loader: async ({ params, abortSignal }) => {
+      const response = await fetch(`/api/users/${params.id}`, { signal: abortSignal });
+      if (!response.ok) throw new Error('Network error');
+      return response.json();
+    }
+  });
+
+  // Use the resource value in computed signals
+  userName = computed(() => {
+    if (this.userResource.hasValue()) {
+      return this.userResource.value()?.name;
+    } else {
+      return 'Loading...';
+    }
+  });
+}
+```
+
+## Aborting Requests
+
+If the `params` signal changes while a previous loader is still running, the `Resource` will attempt to abort the outstanding request using the provided `abortSignal`. **Always pass `abortSignal` to your `fetch` calls.**
+
+## Reloading Data
+
+You can imperatively force the resource to re-run the loader without the params changing by calling `.reload()`.
+
+```ts
+this.userResource.reload();
+```
+
+## Resource Status Signals
+
+The `Resource` object provides several signals to read its current state:
+
+- `value()`: The resolved data, or `undefined`.
+- `hasValue()`: Type-guard boolean. `true` if a value exists.
+- `isLoading()`: Boolean indicating if the loader is currently running.
+- `error()`: The error thrown by the loader, or `undefined`.
+- `status()`: A string constant representing the exact state (`'idle'`, `'loading'`, `'resolved'`, `'error'`, `'reloading'`, `'local'`).
+
+## Local Mutation
+
+You can optimistically update the resource's value directly. This changes the status to `'local'`.
+
+```ts
+this.userResource.value.set({name: 'Optimistic Update'});
+```
+
+## Reactive Data Fetching with `httpResource`
+
+If you are using Angular's `HttpClient`, prefer using `httpResource`. It is a specialized wrapper that leverages the Angular HTTP stack (including interceptors) while providing the same signal-based resource API.