chore: import upstream snapshot with attribution

skills/angular-developer/references/inputs.md

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+# Inputs
+
+Inputs allow data to flow from a parent component to a child component. Angular recommends using the signal-based `input` API for modern applications.
+
+## Signal-based Inputs
+
+Declare inputs using the `input()` function. This returns an `InputSignal`.
+
+```ts
+import {Component, input, computed} from '@angular/core';
+
+@Component({
+  selector: 'app-user',
+  template: `<p>User: {{ name() }} ({{ age() }})</p>`,
+})
+export class User {
+  // Optional input with default value
+  name = input('Guest');
+
+  // Required input
+  age = input.required<number>();
+
+  // Inputs are reactive signals
+  label = computed(() => `Name: ${this.name()}`);
+}
+```
+
+### Usage in Template
+
+```html
+<app-user [name]="userName" [age]="25" />
+```
+
+## Configuration Options
+
+The `input` function accepts a config object:
+
+- **Alias**: Change the property name used in templates.
+- **Transform**: Modify the value before it reaches the component.
+
+```ts
+import { input, booleanAttribute } from '@angular/core';
+
+@Component({...})
+export class CustomButton {
+  // Alias example
+  label = input('', { alias: 'btnLabel' });
+
+  // Transform example using built-in helper
+  disabled = input(false, { transform: booleanAttribute });
+}
+```
+
+## Model Inputs (Two-Way Binding)
+
+Use `model()` to create an input that supports two-way data binding.
+
+```ts
+@Component({
+  selector: 'custom-counter',
+  template: `<button (click)="increment()">+</button>`,
+})
+export class CustomCounter {
+  value = model(0);
+
+  increment() {
+    this.value.update((v) => v + 1);
+  }
+}
+```
+
+### Usage
+
+```html
+<!-- Two-way binding with a signal -->
+<custom-counter [(value)]="mySignal" />
+
+<!-- Two-way binding with a plain property -->
+<custom-counter [(value)]="myProperty" />
+```
+
+## Decorator-based Inputs (@Input)
+
+The legacy API remains supported but is not recommended for new code.
+
+```ts
+import { Component, Input } from '@angular/core';
+
+@Component({...})
+export class Legacy {
+  @Input({ required: true }) value = 0;
+  @Input({ transform: trimString }) label = '';
+}
+```
+
+## Best Practices
+
+- **Prefer Signals**: Use `input()` instead of `@Input()` for better reactivity and type safety.
+- **Required Inputs**: Use `input.required()` for mandatory data to get build-time errors.
+- **Pure Transforms**: Ensure input transform functions are pure and statically analyzable.
+- **Avoid Collisions**: Do not use input names that collide with standard DOM properties (e.g., `id`, `title`).