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/tools.md

@@ -0,0 +1,40 @@
+# Tool Registration
+
+## Interface
+
+```typescript
+// Without agent context
+api.registerTool({
+  name: "my-tool",
+  description: "Does something",
+  inputSchema: {
+    type: "object",
+    properties: {
+      param: { type: "string", description: "..." },
+    },
+    required: ["param"],
+  },
+  execute: async (toolCallId, params) => {
+    const { param } = params as { param: string };
+    return { result: "ok" };
+  },
+});
+
+// With agent context (factory function)
+api.registerTool((ctx) => ({
+  name: "my-contextual-tool",
+  description: "...",
+  inputSchema: { /* ... */ },
+  execute: async (toolCallId, params) => {
+    const agentId = ctx.agentId;
+    return { result: agentId };
+  },
+}));
+```
+
+## Key Points
+
+- Interface is `execute: async (toolCallId, params)`, NOT `handler:`
+- Use `inputSchema` (JSON Schema), NOT `parameters`
+- Return `{ result: "..." }` object
+- Factory form `(ctx) => ({...})` gives access to agent context (agentId, sessionKey, etc.)