docs: add provider hub and model provider pages

docs/providers/opencode.md

@@ -0,0 +1,34 @@
+---
+summary: "Use OpenCode Zen (curated models) with Clawdbot"
+read_when:
+  - You want OpenCode Zen for model access
+  - You want a curated list of coding-friendly models
+---
+# OpenCode Zen
+
+OpenCode Zen is a **curated list of models** recommended by the OpenCode team for coding agents.
+It is an optional, hosted model access path that uses an API key and the `opencode` provider.
+Zen is currently in beta.
+
+## CLI setup
+
+```bash
+clawdbot onboard --auth-choice opencode-zen
+# or non-interactive
+clawdbot onboard --opencode-zen-api-key "$OPENCODE_API_KEY"
+```
+
+## Config snippet
+
+```json5
+{
+  env: { OPENCODE_API_KEY: "sk-..." },
+  agents: { defaults: { model: { primary: "opencode/claude-opus-4-5" } } }
+}
+```
+
+## Notes
+
+- `OPENCODE_ZEN_API_KEY` is also supported.
+- You sign in to Zen, add billing details, and copy your API key.
+- OpenCode Zen bills per request; check the OpenCode dashboard for details.