feat: add /ego-mgr slash command and rename pcexec to pc-exec

Changes:
1. Add /ego-mgr slash command with subcommands:
   - get, set, list, delete, add-column, add-public-column, show
   - Uses pcExec to call ego-mgr binary with proper env vars

2. Rename pcexec → pc-exec throughout codebase:
   - Tool name: pcexec → pc-exec
   - Function exports: pcexec → pcExec, pcexecSync → pcExecSync
   - Updated all references in skills and plugin files

3. Translate all Chinese text to English:
   - ego-mgr-slash.ts responses
   - slash-commands.ts responses
   - SKILL.md files remain in English

plugin/openclaw.plugin.json

@@ -2,7 +2,7 @@
   "id": "padded-cell",
   "name": "PaddedCell",
   "version": "0.2.0",
-  "description": "Secure password management, safe execution, and coordinated agent restart",
+  "description": "Secure secret management, agent identity management, safe execution, and coordinated agent restart",
   "entry": "./index.js",
   "configSchema": {
     "type": "object",