docs: add OpenCode CLI integration guide (#169)

- Added OpenCode section to README.md CLI Integration with step-by-step instructions
- Uses @ai-sdk/openai-compatible adapter with custom opencode.json config
- Includes example models and baseURL configuration
- Closes #169

README.md

@@ -1095,6 +1095,47 @@ Settings → API Configuration:
   Model: if/kimi-k2-thinking
 ```
 
+### OpenCode
+
+**Step 1:** Add OmniRoute as a custom provider:
+
+```bash
+opencode
+/connect
+# Select "Other" → Enter ID: "omniroute" → Enter your OmniRoute API key
+```
+
+**Step 2:** Create/edit `opencode.json` in your project root:
+
+```json
+{
+  "$schema": "https://opencode.ai/config.json",
+  "provider": {
+    "omniroute": {
+      "npm": "@ai-sdk/openai-compatible",
+      "name": "OmniRoute",
+      "options": {
+        "baseURL": "http://localhost:20128/v1"
+      },
+      "models": {
+        "cc/claude-sonnet-4-20250514": { "name": "Claude Sonnet 4" },
+        "gg/gemini-2.5-pro": { "name": "Gemini 2.5 Pro" },
+        "if/kimi-k2-thinking": { "name": "Kimi K2 (Free)" }
+      }
+    }
+  }
+}
+```
+
+**Step 3:** Select the model in OpenCode:
+
+```bash
+/models
+# Select any OmniRoute model from the list
+```
+
+> **Tip:** Add any model available in your OmniRoute `/v1/models` endpoint to the `models` section. Use the format `provider/model-id` from your OmniRoute dashboard.
+
 </details>
 
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