feat: add openclaw-plugin-dev skill

Plugin development reference and workflows based on real development
experience (Dirigent, ContractorAgent, PrismFacet).

Docs: structure, entry-point, hooks, tools, state, config, debugging
Workflows: create-plugin, add-hook

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

openclaw-plugin-dev/docs/config.md

@@ -0,0 +1,61 @@
+# Config Schema & Install Scripts
+
+## openclaw.plugin.json
+
+```json
+{
+  "$schema": "https://openclaw.ai/schemas/plugin-config.json",
+  "configSchema": {
+    "type": "object",
+    "additionalProperties": false,
+    "properties": {
+      "myToken": { "type": "string" },
+      "myFlag": { "type": "boolean", "default": false }
+    }
+  }
+}
+```
+
+### Rules
+
+- `additionalProperties: false` is mandatory — OpenClaw validates config against schema
+- Removing a config field requires removing it from schema too (or gateway fails to start)
+- Sensitive fields (tokens, keys): no `default`, user must configure manually
+
+## Install Script (scripts/install.mjs)
+
+### Install does:
+
+1. Build dist (compile TypeScript)
+2. Clean and copy to `~/.openclaw/plugins/<id>/`
+3. Update `openclaw.json`:
+   - Add to `plugins.allow`
+   - Add to `plugins.load.paths`
+   - Set `plugins.entries.<id>.enabled = true`
+   - Set default config via `setIfMissing` (never overwrite existing values)
+4. Never set sensitive fields (tokens) — add comments for manual configuration
+
+### Uninstall does:
+
+1. Remove from `plugins.allow`
+2. Delete `plugins.entries.<id>`
+3. Remove from `plugins.load.paths`
+4. Delete install directory
+
+### setIfMissing pattern
+
+```javascript
+function setIfMissing(obj, key, value) {
+  if (obj[key] === undefined || obj[key] === null) {
+    obj[key] = value;
+  }
+}
+```
+
+### Config field changes
+
+When renaming or removing config fields:
+1. Update `openclaw.plugin.json` schema first (source of truth)
+2. Update `normalizeConfig()` in index.ts
+3. Update install script `setIfMissing` calls
+4. Document migration steps for users