feat: Add OpenClaw as conversion target

Add openclaw as the 8th conversion target, enabling:
  bunx @every-env/compound-plugin install compound-engineering --to openclaw

Converts Claude Code plugins into OpenClaw's extension format:
- Agents → skills/agent-*/SKILL.md
- Commands → api.registerCommand() + skills/cmd-*/SKILL.md
- Skills → copied verbatim with path rewriting (.claude/ → .openclaw/)
- MCP servers → openclaw.json config
- Generates openclaw.plugin.json manifest, package.json, and index.ts entry point

Output installs to ~/.openclaw/extensions/<plugin-name>/

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/commands/install.ts

@@ -25,7 +25,7 @@ export default defineCommand({
     to: {
       type: "string",
       default: "opencode",
-      description: "Target format (opencode | codex | droid | cursor | pi | copilot | gemini | kiro)",
+      description: "Target format (opencode | codex | droid | cursor | pi | copilot | gemini | kiro | openclaw)",
     },
     output: {
       type: "string",
@@ -195,6 +195,9 @@ function resolveTargetOutputRoot(
     const base = hasExplicitOutput ? outputRoot : process.cwd()
     return path.join(base, ".kiro")
   }
+  if (targetName === "openclaw") {
+    return path.join(os.homedir(), ".openclaw", "extensions", "compound-engineering")
+  }
   return outputRoot
 }