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/entry-point.md

@@ -0,0 +1,49 @@
+# Plugin Entry Point
+
+## Format
+
+```typescript
+import type { OpenClawPluginApi } from "openclaw/plugin-sdk";
+
+const _G = globalThis as Record<string, unknown>;
+const LIFECYCLE_KEY = "_myPluginGatewayLifecycleRegistered";
+
+export default {
+  id: "my-plugin",
+  name: "My Plugin",
+  register(api: OpenClawPluginApi) {
+    const config = normalizeConfig(api);
+
+    // Gateway lifecycle: only once
+    if (!_G[LIFECYCLE_KEY]) {
+      _G[LIFECYCLE_KEY] = true;
+      // Start sidecars, init global resources
+      api.on("gateway_stop", () => { _G[LIFECYCLE_KEY] = false; });
+    }
+
+    // Agent session hooks: every register() call (dedup inside handler)
+    registerMyHook(api, config);
+
+    // Tools
+    registerMyTools(api, config);
+
+    api.logger.info("my-plugin: registered");
+  },
+};
+```
+
+## Why globalThis?
+
+OpenClaw may hot-reload plugins. Module-level variables reset on reload, but `globalThis` persists. All mutable state must be on `globalThis`:
+
+- Startup flags → prevent double initialization
+- Dedup sets → prevent double hook execution
+- Runtime references → keep connections alive across reloads
+- Shared registries → preserve cross-plugin state
+
+## Naming Convention
+
+```
+_<pluginId>PluginXxx     # Internal state (e.g., _prismFacetRouters)
+__<pluginId>             # Cross-plugin public API (e.g., __yonexusClient)
+```