docs: convert all skill instructions from npm to pnpm

Batch update 62 files across .claude/skills/ — SKILL.md, REMOVE.md,
and script files. Conversions: npm run -> pnpm run, npm install ->
pnpm install, npx -> pnpm exec/dlx, npm uninstall -> pnpm uninstall,
package-lock.json -> pnpm-lock.yaml, shebangs updated.

.claude/skills/x-integration/host.ts

@@ -22,7 +22,7 @@ async function runScript(script: string, args: object): Promise<SkillResult> {
   const scriptPath = path.join(process.cwd(), '.claude', 'skills', 'x-integration', 'scripts', `${script}.ts`);
 
   return new Promise((resolve) => {
-    const proc = spawn('npx', ['tsx', scriptPath], {
+    const proc = spawn('pnpm', ['exec', 'tsx', scriptPath], {
       cwd: process.cwd(),
       env: { ...process.env, NANOCLAW_ROOT: process.cwd() },
       stdio: ['pipe', 'pipe', 'pipe']