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/migrate-from-openclaw/MIGRATE_CRONS.md

@@ -68,7 +68,7 @@ Source: `src/db.ts`
 Insert directly into the SQLite database. This requires groups to be registered first (Phase 1). Use the registered group's `folder` and `chat_jid`:
 
 ```bash
-npx tsx -e "
+pnpm exec tsx -e "
 const Database = require('better-sqlite3');
 const { CronExpressionParser } = require('cron-parser');
 const db = new Database('store/messages.db');