feat: refactor project structure + add pcguard + AGENT_VERIFY injection

- Restructure: pcexec/ and safe-restart/ → plugin/{tools,core,commands}
- New pcguard Go binary: validates AGENT_VERIFY, AGENT_ID, AGENT_WORKSPACE
- pcexec now injects AGENT_VERIFY env + appends openclaw bin to PATH
- plugin/index.ts: unified TypeScript entry point with resolveOpenclawPath()
- install.mjs: support --openclaw-profile-path, install pcguard, new paths
- README: updated structure docs + security limitations note
- Removed old root index.js and openclaw.plugin.json

plugin/openclaw.plugin.json

@@ -0,0 +1,15 @@
+{
+  "id": "padded-cell",
+  "name": "PaddedCell",
+  "version": "0.2.0",
+  "description": "Secure password management, safe execution, and coordinated agent restart",
+  "entry": "./index.js",
+  "configSchema": {
+    "type": "object",
+    "properties": {
+      "enabled": { "type": "boolean", "default": true },
+      "passMgrPath": { "type": "string", "default": "" },
+      "openclawProfilePath": { "type": "string", "default": "" }
+    }
+  }
+}