fix(builder): escape/allowlist all attribute-value sinks incl. numeric/enum props (XSS)

An adversarial pass found 5 Critical XSS sinks where props declared number/enum
in TypeScript were interpolated raw into exported HTML attribute values,
trusting the type — but nothing enforces it at runtime (AI update_props only
validates node_id; deserialized saved state is untyped JSON). Fixed all 5
(NumberCounter data-target, StarRating aria-label, FormContainer method,
ContactForm/InputField input type) plus 6 sibling sinks found by an exhaustive
audit of every attribute-value interpolation across src/components: a
JS-source injection into ContentSlider's inline setInterval script, a
prototype-pollution-adjacent allowlist gap in Section's divider-shape lookup,
TextareaField rows, Testimonials rating aria-label, HeroSimple textAlign, and
MapEmbed zoom. Adds shared sanitizeFormMethod/sanitizeInputType allowlist
helpers to utils/escape.ts alongside the existing escapeAttr/safeUrl/cssValue
primitives. Every fix is TDD'd: a malicious-value test reproduces the raw
injection against the pre-fix code, then passes after the fix.

502 tests green (npx vitest run), tsc + vite build green (npm run build).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/components/media/ImageBlock.toHtml.test.ts

@@ -0,0 +1,34 @@
+import { describe, test, expect } from 'vitest';
+import { ImageBlock } from './ImageBlock';
+
+const toHtml = (ImageBlock as any).toHtml;
+
+describe('ImageBlock.toHtml src/alt XSS hardening', () => {
+  test('a javascript: src never reaches the output', () => {
+    const { html } = toHtml({ src: 'javascript:alert(1)' }, '');
+    expect(html).not.toContain('javascript:');
+  });
+
+  test('a malicious src cannot break out of the src attribute', () => {
+    const malicious = 'https://example.com/x.jpg" onerror="alert(1)';
+    const { html } = toHtml({ src: malicious }, '');
+    expect(html).not.toContain('onerror="alert(1)"');
+  });
+
+  test('a malicious alt cannot break out of the alt attribute', () => {
+    const malicious = 'x" onerror="alert(1)';
+    const { html } = toHtml({ src: 'https://example.com/x.jpg', alt: malicious }, '');
+    expect(html).not.toContain('onerror="alert(1)"');
+  });
+
+  test('a placeholder/empty src emits no output', () => {
+    const { html } = toHtml({ src: '' }, '');
+    expect(html).toBe('');
+  });
+
+  test('a normal image still renders correctly', () => {
+    const { html } = toHtml({ src: 'https://example.com/photo.jpg', alt: 'A photo' }, '');
+    expect(html).toContain('src="https://example.com/photo.jpg"');
+    expect(html).toContain('alt="A photo"');
+  });
+});