Add russian version

Author: xPaw

AGENTS.md

@@ -0,0 +1,20 @@
+# Translation guidelines
+
+This site has localized pages (e.g. `ru.html`) based on `index.html`.
+
+## Structure
+
+- `index.html` is the English original and source of truth.
+- Translated pages are simplified: no JS, no JSON-LD, no changelog, no libraries/code section, no nav bar.
+- SVG icons, logos, and game icons are copied as-is.
+
+## Translation rules
+
+1. **Do not leave English phrases inline in target-language grammar.** Use proper equivalents in the target language or established transliterations.
+2. **Translate for the target audience, not word-for-word.** Adapt phrasing to sound natural.
+3. **Use established gamedev/tech terminology in the target language.** Prefer terms that the local gamedev community actually uses over obscure native equivalents.
+4. **Some technical names stay in English.** Product names, file extensions, library name, and format names are not translated.
+
+## When updating translations
+
+After any content change to `index.html`, check if translated pages need corresponding updates.

index.html

@@ -7,6 +7,9 @@
 		<meta name="theme-color" content="#0c121c">
 		<title>Source 2 Viewer &amp; Decompiler</title>
 		<link rel="canonical" href="https://s2v.app/">
+		<link rel="alternate" hreflang="en" href="https://s2v.app/">
+		<link rel="alternate" hreflang="ru" href="https://s2v.app/ru.html">
+		<link rel="alternate" hreflang="x-default" href="https://s2v.app/">
 		<link rel="image_src" href="https://s2v.app/static/preview.jpg">
 		<link rel="preload" href="static/Manrope.woff2" as="font" type="font/woff2" crossorigin>
 		<link rel="preconnect" href="https://api.github.com">
@@ -608,7 +611,7 @@ <h3>Audio System</h3>
 					<h3>Shader Packages</h3>
 					<ul>
 						<li>
-							Inspect and analyze Source 2<a href="/ValveResourceFormat/api/ValveResourceFormat.CompiledShader.html">shader files</a>
+							Inspect and analyze Source 2 <a href="/ValveResourceFormat/api/ValveResourceFormat.CompiledShader.html">shader files</a>
 							(vcs extension) with bytecode conversion
 						</li>
 						<li>Read Source 2 shader packages</li>