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/hooks.md

@@ -0,0 +1,62 @@
+# Hook Registration
+
+## Available Hooks
+
+| Hook | Purpose | Dedup Method |
+|------|---------|-------------|
+| `before_model_resolve` | Override model/provider before LLM call | WeakSet on event |
+| `before_prompt_build` | Inject into system prompt | WeakSet on event |
+| `before_agent_start` | Legacy prompt injection | WeakSet on event |
+| `agent_end` | Post-conversation actions | Set on runId |
+| `message_received` | React to inbound messages | — |
+| `llm_input` / `llm_output` | Observe LLM traffic | — |
+| `before_tool_call` / `after_tool_call` | Observe tool execution | — |
+| `gateway_start` / `gateway_stop` | Gateway lifecycle | globalThis flag |
+
+## Dedup Patterns
+
+### WeakSet (for event-object hooks)
+
+```typescript
+const _G = globalThis as Record<string, unknown>;
+const DEDUP_KEY = "_myPluginHookDedup";
+if (!(_G[DEDUP_KEY] instanceof WeakSet)) _G[DEDUP_KEY] = new WeakSet<object>();
+const dedup = _G[DEDUP_KEY] as WeakSet<object>;
+
+api.on("before_model_resolve", async (event, ctx) => {
+  if (dedup.has(event as object)) return;
+  dedup.add(event as object);
+  // ... handler logic
+});
+```
+
+### Set with runId (for agent_end)
+
+```typescript
+const DEDUP_KEY = "_myPluginAgentEndDedup";
+if (!(_G[DEDUP_KEY] instanceof Set)) _G[DEDUP_KEY] = new Set<string>();
+const dedup = _G[DEDUP_KEY] as Set<string>;
+
+api.on("agent_end", async (event, ctx) => {
+  const runId = (event as any).runId as string;
+  if (runId) {
+    if (dedup.has(runId)) return;
+    dedup.add(runId);
+    if (dedup.size > 500) dedup.delete(dedup.values().next().value!);
+  }
+  // ... handler logic
+});
+```
+
+## Prompt Injection Hooks
+
+`before_prompt_build` and `before_agent_start` can return prompt mutation fields:
+
+| Field | Caching | Use for |
+|-------|---------|---------|
+| `prependSystemContext` | Cached | Static role/identity prompts |
+| `appendSystemContext` | Cached | Static supplementary guidance |
+| `prependContext` | Not cached | Per-turn dynamic context |
+| `systemPrompt` | — | Full system prompt replacement (rarely used) |
+
+Requires `plugins.entries.<id>.hooks.allowPromptInjection: true` in openclaw.json.