Add portable OpenCode config bundle for Linux and Windows

.env.example

@@ -0,0 +1,9 @@
+# Copy to .env and fill locally. Never commit your real keys.
+
+OPENROUTER_API_KEY=
+OPENCODE_ZEN_API_KEY=
+V0_API_KEY=
+GITHUB_TOKEN=
+ANTHROPIC_API_KEY=
+OPENAI_API_KEY=
+GOOGLE_API_KEY=